Overall, Smash 4's online experience is mostly worse than Brawl for numerous reasons, despite some great innovations. I will list the pros and cons of this version over Brawl:
Pros:
+ Spectator mode is greatly improved over Brawl, despite the frequent repeat matches which are great for accumulating gold.
+ Ability to report and ban taunt parties which plagued Brawl
+ 1 vs. 1 stock matches With Anyone
+ Groups form much faster with far less time spent in waiting room
Cons:
- Ridiculous input lag (over 500 ms) With Anyone about a quarter of the time
- No ability to choose stages With Anyone
- No ability to remove items in For Fun
- No Battlefield or Smashville in For Glory
- No co-op modes online (I miss Multi-man Brawl, Home Run contest, etc.)
- No Regional matches With Anyone to limit latency (a la Kart 8)
- No ability to use Mii fighters With Anyone
- No ability to send replays to friends
I could go on and on, but the disappointments are numerous enough to say that Smash 4's online experience is mostly a downgrade from Brawl, which never suffered input lag, despite some terribly choppy matches it had. This happens even on an ancient traditional tube TV, so I blame the lack of forced regional matches. Quite frankly, the speed of light is too slow to fight internationally. The laws of physics simply make it infeasible. Give us an option to restrict matches to Regional, as we already can in Kart, and this greatly diminish input lag. Also give us back the online co-op modes that Brawl had. I miss those features greatly.