Both, lately. In Melee I'd always choose random but get happy with Doc or Zelda. In VF4 I'd always choose Aoi. I've been playing SSFIV lately and have been sticking to Dudley so I can get good with him, but I like playing as a random character as well, as it lets you learn about different movesets and such.
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chumbucketeer fills cups like double-Ds.
http://img.imgcake.com/chumpngej.png - Art by BIGPUN9999