In regards to ATI vs. nVidia, new product offerings from ATI made me switch from nVidia. The HD 5850 is a bargain of a card, and it was cheaper than my $300 budget for a gaming video card. The only gripe I have with ATI is the Catalyst Control Center, but I don't notice any issues with the SSD haha.
Seriously, though... I switched back and forth looking for performance bargains as well as power efficiency.
ATI 9700Pro -> GeForce 256 -> X800XL ->X1800GTO2 -> 8800GT G92 -> 8800GTS G92 -> HD 5850... that's everything I've owned since 2000.
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