Well, it depends. The story hasn't changed. But, there're supposedly tons of minor updates to the online fighting and balancing.
That said, as a casual player, unless you want the extra outfits for the female fighters, I think it's all fluff.
I never took this game seriously, though, as there's just too much juggling (pun intended) and opportunities for button mashing.
They are laser targeting one demographic with their 'new outfits'/DLC(don't think they even bother with the guys outfits anymore),