I would say EVGA since it's factory overclocked. If you overclock a card you buy it voids the warranty.
Completely untrue. Asus and EVGA will allow you to overclock within reason, obviously if you up the voltage too much and send one back with fried VRMs they'll ask questions but generally they allow it. EVGA even go as far to let you install custom coolers as long as it wasn't the cause of the damage and you return it with the factory cooler re-installed. Read the T&C's! As long as you do things right your in good hands with both companies.
The Asus is also factory OC'd and id probably still take the non TOP version over the EVGA but its a close enough call, both are great.