I've only ever played Persona 5 Royal so will go with that. I doubt any of the other Persona's can top it anyways.
The game was amazing.

As for Persona 6, I expect it to be on PS4 and PS5.
Im hopeful for a Switch version or Switch successor at least. The game is perfect for handheld.

It's between P3/P4 on paper not so different from each other but if you played them you know they are different enough especially story wise (duh). Which one I prefer depends on my memories and my mood.

Bonus question. I don't think I will ever play a Persona game again, I feel I have to play them with guide so I make the right decisions and I like to complete everything but it is so draining for me to do it with a Persona game it stresses me out and at moments may feel like work.

I actually played them in reverse order. Started with 5 then 4G then 3FES and I enjoyed 3 the most, closely followed by P5 and P4G the least (loving all of them though). I haven't played 1 or 2 and honestly the only way I will play them is if Atlus decides to remake or remaster them.

I have nothing but high expectations for Persona 6. I would say I expect it to be on multiple platforms (PS5, PC, and Switch) but Atlus did make SMTV Switch only so I could see them doing PS5 only for Persona 6 and then a delayed port for PC a year or two later. 

Close call between 3 and 4. 3 was my first Persona game and I really enjoyed all of the characters and the story but I lean 4. I haven't played the psv remakes of 3 and 4 and keep hoping they show up on PSN or Switch at some point.

So I've played Persona 4 Golden, Persona 5 Royal, and Persona 5 Strikers. All this year, by the way. I want to play 3, but I'm holding out hope for a PS4/PS5 port or remake. I do own a Vita, so maybe I could just play the PSP version if Atlus doesn't plan to bring it to newer platforms.
Persona 5 Royal is my fave. I'm also going to go against the grain here and say that I really love Persona 5 Strikers as well. For what shortcomings it has over Persona 5 (Vanilla or Royal), it has almost as many strengths. I really loved the summer vacation road trip plot, I also think Persona 5 might be too long, whereas Strikers doesn't have that issue.
I love Persona 4 Golden a lot as well. It's the first one in the series I played, and it was nice playing one of the Vita's flagship titles. Golden was exclusive to Vita for almost 8 years, but thankfully there is a PC release. I did play it on Vita, though.
I don't think I'll ever get around to Persona or the two games of Persona 2. I just don't know if I'll like them very much. Or even if I do like them, I might not even be able to beat them. I haven't beat any RPGs that are tougher than Xenoblade Chronicles or the Mother trilogy.
I really hope we get Persona 6 formally announced soon. The earliest I could see it releasing is 2023. It will almost surely be on PS5, but who knows if there will be a PS4 version.

Persona 4 Golden/ Best game in the series. I like 5 a lot but aside from a slicker presentation, it's not as good. Badly-paced game. Not a fan of the dungeons. I liked P5 a lot but I enjoyed Tokyo Mirage Sessions more and think it's a better successor to P4 directly dungeons-wise.

Haven't played Persona 1 nor the Persona 2 duology, also not gonna bother talking about the spinoffs cause they're their own thing not worth comparing to the mainline games. My thoughts are going to be all over the place so don't expect anything concise or well written lol.

Persona 3: The main combat can come off as clunky and outdated, primarily because you can't control your party members which can be a little eh. I don't think it's honestly a huge issue though outside of a few bosses, since you can still influence what they do with the command system, so you can still basically tell them to attack, use healing/buffs/debuffs, or just do nothing. The social link system in this game is also really strict, especially since the level up upgrades and Personas you can fuse once you max out a social link are pretty damn vital if you want to beat the game. Not helping things is the fact that if you neglect a social link for too long, or you say the wrong thing during a social link, you can end up blocking yourself off from the social link, which causes you to waste time just to be able to resume them. I honestly resorted to a guide for social links near the end, cause nothing is really stopping you from constantly saving and reloading an older save if things go south, and it can get a bit stressful. You also gotta juggle social links with maxing out your social stats, as you won't be able to progress some social links without them. They're fairly straight forward to max out though, even if knowledge takes forever. Despite all that, fusing the Personas you get access to after the social links is a really rewarding feeling, especially since some of the late game spells you get deal massive damage and are really satisfying to use. The story takes awhile to get remotely interesting, and I didn't really care for anything or anyone at first, but when a certain robot makes their appearance, and especially when THAT guy shows up, yea it gets really good. Overall a great game, but I don't like the social simulator part of this game that much. Also the music slaps.

Persona 4: I only played Golden, and from what I've heard the overall difficulty in the original is better balanced, in a game that is considered significantly easier than Persona 3. I played on normal in Golden on my first playthrough, and yea the game is a little too easy; I recall being able to brute force my way through some bosses without really using buffs/debuffs that much and I never really felt close to dying. If you're playing this game on PC for the first time, you can play around with the difficulty modifier if things feel off, which is a nice feature. As for the game itself, they removed the penalty for neglecting them for too long, so I'm glad they removed that source of stress. I feel it's balanced out now that there's five social stats to max out instead of three, though it takes just as long to max them out as 3's I feel. Other QoL features like being able to control your party members and being able to choose what skill fused Personas end up inheriting (in Golden at least) are also appreciated. Despite these small refinements, I don't feel like they impact my enjoyment of this game that much to the point where I'd say I like this game way more than Persona 3; at worst I need to think more when it comes to the social links in 3. The story in Persona 4 has slightly better pacing in my opinion, and I like the main villain of most of the story, but Persona 3's story had more stakes and suspense, and I feel the final acts of 3 just made it way more memorable, but I still think 4 is a fun ride overall. I like 4 as much as 3. Also the music is pretty good.

Persona 5: The confidant system feels the most refined here I say, and while some people might say it's not as deep as 3's without the penalties and whatnot, I can do without them. The social stats system is more or less the same as 4's, though it's probably the easiest to max out here, since you get a lot more opportunities to do so, including from just doing confidants. The combat is also the best here I feel, with the animations really selling the power of attacks, especially your standard melee attack. I feel it's also the easiest, or at least most convenient in this game to not only fuse the Personas you want, but also inherit the skills you want to truly get some strong builds, and it's pretty satisfying to be decked out with strong Personas towards the end. The dungeons being replaced with palaces with their set layouts, puzzles, and gimmicks is a neat change, and with the exception of one of them, they're all designed well I feel. The stealth mechanic is a new mechanic that sorta just exists, without adding much substance, but it's harmless at worst. The story is pretty good overall; one story arc around the beginning of the second half is pretty bad, but the climax and ending are fantastic, though not as memorable as 3 for me. Royal adds some neat stuff, most notably a couple more main characters and an extra story arc, with one of those characters being one of the best characters in the series I feel. It feels little tacked on though, and while it's great stuff, it does somewhat detract from the original already having a good ending. 5 is a great game overall, and my favorite of the ones I've played. Also the music is filled with bangers.

No real hopes with 6, I'd like to see an adult cast like they did with 2 I guess, and I'd prefer a rural setting like with 4. No reason why the next Persona game shouldn't be multi-plat at this point, unless Sony just wants to have their iron grip on this supposed exclusivity contract they have on the mainline games. At the very least it should be PS5 and PC.

What exactly you dislike about P5 dungeons? I'm curious because for me they are flawless

Too long and you can't complete them in one go.

Sure thing. But that's a plus