Honestly I don't think either game will be better than the other. I've never played a bad Megami-Tensei game, and I've played at least one from each sub-series. There is no reason to suspect Revelations to be a boring and generic game. It looks pretty unique in world design for an SMT game. Having said that, Persona 5 gives me Dark than Black vibes with its style and animation (which brings a lot of nostalgia) and of course the game-play is already well known.

one thing for sure spin off game will never top the annual series games, so i guess persona will have lead because of that, it will be different though if SMT series coming to Wii U then it will be hard to decide.

Yet all modern MT games are collections of MT spin-offs, so it makes very little sense to say a spin-off can't be as good as an established sub-series. This game obviously has a budget comparable to other MT games. I mean, Persona started off as an MT spin-off, "Megami Ibunroku Perusona.^" 

Furthermore spin-off SMT games like Digital Devil Saga, Devil Summoner, Devil Survivor, etc aren't too far off from the quality of main series SMT games like Nocturne - for some people they are better. 

I was never on a side. Just critical. I haven't changed my mind about it, but nothing's just black or white.

It's still too early to judge, we need more information. We don't even know how the social part of P5 will be and if SMTxFE will have a social side at all, which is very important imo. I think they'll both be great games, but right now I'm more hyped for P5 simply because I'm a Persona fan and I've never played a FE game, so the fanservice has 0 value to me.

True. Too bad that's not what they gave us.

Then SMT X FE will be spin off on top of spin off lol, there is no close relation between two games lol , but i am still believe it will be pure fan service rather then gameplay quality, and also story will be hard to combine between this two games on SMT X FE,   but then again we only have small clue on how SMT X FE gameplay mechanisme look like.

What exactly is it a spin-off of? It seems to me as if it is an original megami tensei game with fire-emblem's mythology mixed in. We saw actual gameplay, it is obvious that it isn't "pure-fanservice. 

^ What we can see from these screens. Quality, large world to explore. Decent-looking active-time-battle combat system. A mix of SMT and Fire-Emblem mythology. Sure, there will be some fan-service, but not "purely fanservice." 

People still debating this?

Personally it looks like they heavily borrowed elements from their most successful SMT series, Persona, and added a twist to it. Obviously this'll disappoint the hardcore SMT community but I doubt Atlus cares. This could be Atlus' answer to Persona for Nintendo platforms. The FE elements still havent been shown but its safe to say FE fans are emotionally damaged by the trailer.

Probably won't do amazing, but could evolve into something unique and interesting with its own identity over time.

Persona fan will give u this question, " so what is special with this games ??? what makes this game will be different from Persona or SMT series, most people  already comfortable with Persona series and their improve gameplay system.  SMT X FE will look like Persona games or SMT with FE character Fan service and un related stories which is totally spin off of spin off.  while FE loyal fan will ask you " where is FE mechanic on this game"?.