I think that the Coralvue is a brighter bulb as far as light level and intensity. But this is a very subjective opinion. I don't have any "hard data" to back this up and someone could easily say that the XM is infact the brighter bulb. Again, I think both are excellent bulbs and you will be happy with either pick. The XM's are typically cheaper so that makes them even more attractive.
Both run around the same temperature so that makes no difference.