Z77 Extreme 4 since it is an ATX board and is higher class (more features) than the PRO3. The Extreme4M is a mATX board which means less expansion slots to begin with.
Z77 Extreme 4 since it is an ATX board and is higher class (more features) than the PRO3. The Extreme4M is a mATX board which means less expansion slots to begin with.