ATI cards have a tenancy to react lets say "half heatedly" to normal circumstances.
What are you talking about? ATI cards are great, a couple of years ago they may not have been as good as Nvidia but right now they are pretty close. And under normal circumstances they work just fine, I'm using an ATI HD 4850 and it's working fine right now, and it works fine in any game I have played with it. ATI may not have the most powerful GPU out right now but that does not mean they react "Half heatedly" under normal circumstances.
It would also be a good idea check benchmarks before you say one thing is better then the other, the 4830 and the 9800GT are almost equal but the 4830 is $30 less for the cheapest version of both cards. Also ATI just released a new set of drivers for the 4830 which has some good performance gains so the games it was behind in should be better.
W/e though get what you want, if you are particular to a company then buy from them; but remember things change in the computer world and brands that were top of the line 5 years ago or even a month ago may not be top of the line today.