I would suggest Project M instead of SSB4.
Reasons:
Can run on PC and Wii (maybe even Wii U)
Also supports online
More skill-based (more technical moves that can be done)
More fluid (less input delay)***
More technical (i.e. wavedashing, L-cancelling, etc)
Harder to be good at (gap between professional players and new players is lessened in SSB4)
More tournament-based (characters are less OP on average, save for Fox, Falco, and Ike)
No OP custom characters (cannot make characters as good as you want them to be)
Sheik's down-air doesn't fling you off the edge like an aerial Falcon Kick (i cri evrtim)
Aside from those, SSB4 has 8-player smash, better graphics, and more maps.
Also, PM runs off of an SD card, in conjunction with SSBB.
*** This is in my experience with both games.