Prestige & Skid Row
I appreciate cracking groups who have a decent cracktro and don't mess up a game with useless trainers and own credits.
Cracktro-wise, I like Prestige for their original intros. Especially their cracktro for Mortal Kombat 2 is fantastic. It features a tunnel, like seen on the highscoretable of Super Stardust. The accompanying music has a soothing ambient beat.
Skid Row-cracks are generally very stable i.e. you don't get a Guru meditation if you play a game for too long and their Cracktros are generally good. So my vote goes for Skid Row.