Both of these guys are hardcore in different areas. Bauer is tough as nails, and can get the job done come hell or high water. And, yes, he'll do it fast. Bristow on the other hand, has ice water in is veins. You wouldn't want that guy hunting you, and worse yet, you wouldn't want him to find you. Bristow is more low key, more conniving. He works the back channels and has more contacts than the rest of the CIA combined.

I'd hate to face Bauer in a one on one confrontation for sure, but I certainly wouldn't want to meet Bristow in a dark alley if he were out to get me. I think he take pleasure in making people suffer.
Alias s1 and s2 were awesome, better imho than an 24 seasons, but s3 was awful. How did they fuck up Season 3 when they had one of the greatest season cliffhangers in TV history!?! s4 was better, but not nearly as good as the first two, and I have low expectations for s5 with Garner being pregnant in real life and on the show.
BTW, the Season 2 reset came about as a result of the show following the Super Bowl. They thought they could capture a much bigger audience if they basically reset everything, and dumbed things down so that the average fan could get into it better. The show suffered for it in the long run. Ironically, it got it's highest ratings ever this past season following Lost.