For a relative newbie:
Eat one (preferably with a near empty stomach just for the sake of not having to deal with impatience.) Wait an hour, maybe two and decide if you feel good enough to justify saving the other edible for another time.
For an established weedhead:
Eat 'em both at the same time. My edible experiences taught me that I'm not going to feel much of anything at all until I hit the 30-40mg mark with edibles, and even then it's only slightly noticeable. I'm no connoisseur or anything, though, and there's people way more experienced with the edible game on this forum than I am. WAY more experienced.