Mostly Sonics, with the exception being the occasional Tails(fluffy tails, mc tails, teles, etc). If the Sonic has a Tails counterpart, I like playing as the team, since it gives me the feeling of playing as both Sonic and Tails.
Tails is my favorite character, and I used to be mainly a Tails player, but Sonic gives me more of a challenge, and I think playing as him in multiplayer made me a bit better at the game as well.