Having had both of them, first let me say both are excellent tarps. The split rings are a non issue, they are strong and work great. If I had to do it over again and just buy one it would be the cuben tarp. I love the weight, pack size and the built on doors. Although don't forget about the superfly which as I understand it is a BMJ with built on doors, or is it the BMJ is a doorless superfly either way all great tarps.
Beware of the man who owns one gun, he probably shoots it well.