Regular exp is better generally, because you can only gain 3 stats with bexp, and most of the time you'll have better growths than that. But if you wanted, you could just reset until one of the 3 is spd (I think). The main use, I would say, is when you've already capped several stats, so this could let you get all the others, or 3/4 or 3/5 or whatever.