About the only thing the Apollo has going for itself (beside the lower price) is the faster Chip-RAM access.
So if you are into scene demos or other stuff that requires a lot of Chip-RAM access stick with the Apollo. In any other the cas the Blizzard is the card to keep.
As for the XC / MC thingy: XM marked chips are preseries Chips, they are less advanced engeneeringwise and run a lot hotter then the later MC series models, even at 50 MHz.
