If doesn't matter if you have a decent internet connection if the person hosting the game has a crap connection, or they quit and the game is delayed while the host is changed and the map resets. I personally have never found the analogue stick to be anywhere near as precise.
it depends on your definition of "better" however.
if "better" means more effective then its hard to argue, keyboard and mouse allows you to be hugely precise and turn on a 6pence in a split second. No chance of that with a pad.
BUT
my personal definition of better is more enjoyable, and that is a tougher call.
if you play at a desk, keyboard and mouse is fine, however, if you like to game relaxing on the sofa in front of the telly with a beer and some mates as i do, then a control pad is better.
try playing split screen gears of war or halo on the sofa with 2 of you useing a keyboard/mouse.
(also keyboard and mouse is almost tantamount to cheating in a way, a pad sort of puts back some of the limitations of physics, you CANT turnround and headshot someone from 200 yards with a pistol when using a pad like you can with a keyboard/mouse set up.
so as i said, i think it depends on how you like to game, as after all, for most, gaming is about entertainment, not necessarily the most "efficient" system.