Online can make things really hard or really easy for you.
I main Sub-Zero, with Ermac/Smoke as subs.
However due to lag, Ermac is my best character online. His moves can easily catch unguarding opponents off balance, and the lag doesn't hurt him too bad.
Smoke works decent, but Ermac does everything better.
Sub-Zero, my FAVORITE character (I have his fatality tshirt), I can barely play online. I had to resort to hickkicks, uppercuts, and slides to win because lag was so bad. My combos wouldn't go in, ice moves are wayyyy to slow with lag, etc. I hope they fix this =(
I tried to do Away1, 2, iceball, 2, 2, powerslide and it was like...nope.