I've always been a fan of the monster based stock motors. They seem to have good pull and they don't seem to be lacking in speed either.
Some motors will have good rpm, some will have more torque. The monstor based motors have more torque. Good for smaller,twistier tracks.
For a track with flowing corners the motors with more rpm may fair better, as once they are up to speed they have the edge on speed, but they lack low down power.
If you like a brush that lasts a long time, I've used the trinity xxx brushes. You need to use them with a fresh motor though, or they will not sit onto the comm unless they are run in for a long time.
Give the comm a light skim once a meeting and they are fine
I don't tend to change the springs often, usually the stock ones suffice for me.