For Twitch I really like lobosjr for the creative ways he finds to play Souls games, and I like Yukaslegion2 when he plays Souls also, because he does some great PvP matches. But I don't really care when either of these guys play anything other than Souls.
Which brings me to Cohh Carnage, who plays all sorts of stuff every day. He's at something like 2 years+ without a day off. That's something! He also has an awesome community, does loads of giveaways, and engages his audience well.
On YouTube I guess Angry Joe because his reviews are fun and he puts a lot of work into them. He's also pretty fair and usually doesn't bitch about things just for the sake of bitching about things. I can't stand just about everything else he does though. Jim Fucking Sterling son is probably a close 2nd.
Erm Patrick Klepek? I don't watch really any YouTube personalities or anything I just find them irritating. I did see Klepek try to beat the Mario maker levels the Giantbomb guys put up so o guess if he counts that is my vote