one factor is support. if your visiontek card goes bad, you'll have to deal with visiontek. if your ati card goes bad, then you'll have to contact ati. for video cards, i find that it's usually safe to buy off-brand rather than paying a premium for a "retail" brand version.
btw, newegg.com which is a very reputable dealer has the ati radeon 9800 pro for $249 + tax if youre in california plus free shipping. they have the sapphire radeon 9800 pro for $210.
