Regular brushes just don't seem to hold up that well, so I would go with the Orion V2, Checkpoint, or the Cobalt 2/Shock 2 motors. The Orion's probably will last the longest between cuts, and it seems like you end up taking less off when you do have to cut the Orions. The Checkpoints hold up well, and are easier to work on.
I really like the Trinity motors with the oval brushes, they seems to hold up well, are easy to work on, and take "normal" springs. There are 3 different brush compounds available too, so you can go from long wear, to high power.
XXX-CR, XXX-T CR, XXX-SCT (Kertez conversion)
Sneaky Pete Racing