This is a question that plagues me alot at times if I have to go with 1 or the other.

Anyways in the early game(WoB) I usually prefer Edgar he is pretty solid and his machines can really shine there. Once you can learn Bum Rush though I tend to use Sabin more often, bum rushes can hurt a little :rolleyes2

Edgar is still strong in the end game if you built him up and, I guess I go with Sabin just cause I like Bum Rushing :P

Also if you have trouble getting out the blitzes I would definately stick with edgar, if not both are strong, solid characters, so perhaps use one for a bit and then the other and rinse, wash, and repeat.