Windows 7 is what Vista should've been when it was released; but structurally, they're the same. Vista/Windows 7 runs Dolphin much better IMHO.
Custom Desktop -
CPU: Intel Core i5 3570 3.4 GHz to 3.8 GHz (Turbo Boost)
GPU: MSI nVidia GTX 660 2 GB GDDR5
RAM: 8192MB DDR3 SDRAM PC2 10600 1333MHz
OS: Windows 7 Professional 64-bit
HDD: 1 TB Western Digital 7200RPM HDD
CPU: Intel Core i5 3570 3.4 GHz to 3.8 GHz (Turbo Boost)
GPU: MSI nVidia GTX 660 2 GB GDDR5
RAM: 8192MB DDR3 SDRAM PC2 10600 1333MHz
OS: Windows 7 Professional 64-bit
HDD: 1 TB Western Digital 7200RPM HDD