Which one should I buy:
Asus P6T Green with Asus Triton 81 cooler (i7 920,OCZ 6GB 1600Hz)or
Gigabyte EX 58-DS4 with Scythe Mugen 2 cooler (i7 920,OCZ 6GB 1600Hz)
My choice would be the ASUS P6T, as its been shown to have a better BIOS at the moment, giving more stability and options. That may change in the future, but for the moment, ASUS has the lead in my opinion.
Well in that case, I would go with the P6T as that has 3 PCIe sockets so you could Tri-SLI if needed down the road.
I have the ASUS, and if you have double slot cooler GPUS, you cannot go TRI-SLI in this Mobo because you don´t have any free space between the second and third PCI-X x16 slots. It has only 6 SATA and ports and one IDE, if you want more drives to attach you must look for other MoBo (I have this problem 'cause i have a 3 disk RAID 0 array, an a 1TB drive, another 2 Drive RAID 0 array, and a IDE DVD-RW drive ). Otherwise it's a good Mobo, is a good OC and i don´t have any issue with it.