On the subject of the Sonic 3 competition speeds, the problem is that the Sonic 3 Comp levels are much different from the SRB2 levels-after all there were only five levels in Sonic 3.
But you know what, in Sonic 3, if you had to choose one character, it would be Sonic, because Sonic beat Tails and Knuckles on three of the five levels.
The same thing applies to SRB2-if you pick one character, it's Sonic, be it Race or Match. Tails and Knuckles have their moments in some levels and some modes, but if you pick Sonic, your chances are much better. Same as in Sonic 3.