A balance tilted toward understeer (not pushing like a pig, mind) would typically be more stable under braking and in fast turns. Particularly in the latter situation, you let off some throttle and the nose comes back. With an oversteery car, you let off and the back end loosens up. Neither is wrong, but if you don't like the feel of one or the other, you won't have the confidence to push to the limit. I'm sure Ian can expand on this greatly.