If you're only going to get one console this generation I'd say a PS4.

Great exclusives, great third party, variety for days.

Other thing, with $600 you can buy a ps4 and A LOT of games, games like bloodborne, until dawn ,other exclusives and a bunch of third party games cost like $10-$20 these days. SO yeah, go to gamestop.com Here: http://www.gamestop.com/browse/games/playstation-4?nav=28-xu0,131dc-ffff2418-d3 and make a list.

It really depends on your need. I for example really like the games on the PS4 but portablility is a really huge factor for me so I'll probably buy the Switch even if it doesn't have as many games as the PS4. If you prefer playing at home, PS4 is your best bet now.

Well you seem to be a Nintendo fan so that complicates things. Breath of the Wild is phenomenal and I'm sure Metroid Prime 4 is going to be amazing. Arms is a fantastic fighting game despite not being traditional, but it's really only enjoyable with an internet connection as it's 90% online.

That being said when it comes to finical point of view definitely the PS4. For one PS4 games go down in price pretty fast, Switch titles won't be. Nintendo keeps their software prices high for as long as they sell. You will have more games on PS4, more selection, and a fantastic library of must play story based games.

If your a hardcore gamer who wants to play a lot of games then get the PS4. You'll be able to buy 2-3 older games for the price of one Switch title. The PS+ titles are getting better and often have interesting little nicks to try out here and there. Though if portability is a huge factor then the Switch is still a good option. Breath of the Wild easily has 150+ hours worth of content but you might find yourself struggling to buy more games over all.

Will region free be a factor for you? Will you be able to set up a US account on a switch and avoid import taxes? I'm not sure how all that works.

Let us know what you decide to do as I'm curious.

since you talked about 3rd parties and fighting games, it seems like the ps4 is the better choice now.

I'd get a PS4 personally if I was in your situation.

ill defend one aspect of switch:
praticity.
More than just portability and easy plug on tv, tabletop mode is awesome. I play a lot in my bed for hours, holding only the joycon(way less than 3ds). Due to this praticity, im playing much more than with wii U, xbox and 3ds.
I almost cant just play other console anymore, im used to its praticity, id buy every game on switch instead of in other console.
Also, I take it ot the places and i share the play easily, I dont need to previously combine with others take the 3ds with him, we just meet,i show the switch and we play, even if he wasnt left home prepared to play.

Well, but if you doesnt have problem enymore playing on tv only, id recomend ps4.

If you really only get one shot for the next several years, I'd say PS4. That's the safe bet. We know there are tons of great games, and there will be many, many more. With Switch, there are going to be far fewer games to choose from, and we don't even know for sure that the system will be a success. Also, since you're on a limited budget, your money will go a lot further with PS4 games (plus the system will be at least $50 cheaper).

tl;dr - PS4

As much as I love the Switch... it sounds like you would be better off with a PS4 and possibly if you want something portable either look for a cheap vita or a pspgo if you are strapped for cash, a pspgo can be hacked to enjoy all the games on that as long as you can download stuff from the net and know how to use google :) I rarely am an advocate for piracy but at the same time... you have your money saved up that you're going to spend on gaming, there is no magic cash that you aren't giving the industry if you spend all that on a ps4 and games, then get a cheap pspgo.