After a few hours of playing this game, these are my pros and cons:
Pros:
The biggest improvement to the game is the online career mode. You can finally make your own fully customisable character and evolve it.
The ground game is a bit more realistic. They finally added elbows from top and the submission system makes more sense than a stupid mini game.
The characters actually look nicer.
Cons:
The biggest problem I'm having is that the game ironically seems less realistic when it comes to stand up, mostly because of how much they reduced the stamina cost of everything. It almost feels like an arcade game at this point. It seems a lot more beginner friendly. You can throw as much as you can with little to no concern for gassing yourself out, which is very unrealistic, and can't be fixed by some special fx and a doctor interrupting the action almost every fight.
Not a single new tattoo/hair style.
They removed Corey Anderson's fighting stance, which no one else in the game has.
There are about a million different fighting stances, that actually duplicate each other a lot and still aren't too authentic.
Knowing what the game is like, I wouldn't pay that kind of money for it. Thankfully, it was a gift from my friends. Otherwise I'd be disappointed. If you don't care about the online career mode, you're better off sticking to UFC4