Only for Tails, Knuckles actually uses most of the same data branches as Sonic for Competition Mode in the ASM. While some of the shield abilities were cool, I always felt Sonic was like the bare bones 'powerless' character compared to Knuckles and Tails, who had abilities more able to maneuver around different pathways and find secret areas and easter eggs. The difference was especially noticable for water areas, Knuckles and Tails could often evade them altogether, while Sonic was stuck going through them, and naturally lost his shield ability in the process. Even aside from that, at least Knuckles and Tails' moves don't deactivate if they start a new level or get hit once. Knuckles at least had some small balance due to his poor jumping, but even then he was only slightly restricted compared to Sonic, who was vertically challenged at finding different areas to his advantage. Tails more or less had Sonic's strong points plus his game breaking fly ability, and just to point it out could more or less carry one player for a lot of the game in co op mode.