Pick a mix of the two. For specialties where you think you're interested, then pick rotations where you'll learn a lot. But if you pick rotations that are intense for every month, then you risk burning out. So throw in a few chill rotations here and there. Keep in mind, a LOT of it is luck. Rotations you hear great things about, might be your worst rotation. On the other hand, rotations you hear horrible things about might be your best. Therefore, don't get too stressed out over it.