my mobo went recently. i had an intel chipset with an 8800gts 320mb. i had to make a decision. SLI or crossfire potential because i wanted that option.
since ati was doing some catching up in some areas, and i 100% prefer intel chipsets, i went x38 and sold my nvidia card and went with a 3870 so i could run hdmi right out the back of my card to my hdtv with audio. also giving me the chance to add another ati card down the road.
from what i have read, ati seems to scale better across multiple GPU's lately. and yes, while crossfire/sli is not as reliable as powerful single cards the fact is it is an option that can add a ton of power to a lot of games down the road without having to buy the ltaest and greatest card. if you cant afford the best card now, it lets you buy in increments.
most mobos i liked have the 2nd pci express slot near a pci slot, so any double slot cooled GC would eliminate one of the 2 pci slots. while the 8800gt is single slot it is not the best design. the 3870 toxic did have a solid 1 slot design with excellent cooling. so this let me rest at ease knowing i would be able to keep both my pci cards in my machine even if i did go crossfire later.
so i am not saying ati over nvidia, i am just showing an example of all the thoughts that went into such a decision.
for the purest gamer who doesnt oc a ton, maybe an nvidia mobo solution would be best, you wouldnt have to push it so far and find all the memory holes and all that. all you would have on the rig is two Graphics cards so no care for room, etc.
so find out who you are, and go for it!
GOD BLESS US ALL!
if you like OPEN GL games, it is pretty simple, SLI>CROSSFIRE