Go for the MSI cards, they have dual cooling fans which helps to keep your card cool when its gonna be on 24/7. MSI has good warranty too.
I assume you mean Gigabyte. Thanks for the advice.
The XFX 5870 doesnt have voltage control due to XFX being cheap and removing components form the VRM.
EDIT: If you are planning to buy hardware now for mining you most likely didnt understand how bitcoins work.
Reading the reviews, it seems the Gigabyte cards don't have voltage control either, and I'm buying the card primarily for gaming.