Or cast both since they don't share a buff slot with anything else. I do think it would be nice if the devs could give us some solid values and explanations for stuff like this though so we at least know how much they are actually helping.
BTW, enhancing isn't really that hard to skillup. A simple spam macro that you hit every once in a while while watching TV works fine. Something I've noticed is that I do tend to get more magic skillups when targeting another player or enemy. Try afking with a buddy/mule and use that spam macro on him instead of self-targeting and watch the skillups roll in. Healing magic skill has always been the more annoying to cap for me, but you can reduce the annoyance by casting Cure on level appropriate undead family mobs.