nVidia cards are very easy to set up for near optimal performance and require only about 1 hour to fine tune a rig of 6 cards. A 6 card AMD rig will require over 6 hours of time to fine tune and get stable after flashing BIOS.
Having said that, my AMD cards are currently earning 5x the rate of their nVidia counterparts on a $ basis - they just excel when tweaked.
This last December run has seen nVidia outsell AMD for mining.
I agree AMD are more fiddly but the good part is that its fairly easy to find roms both here and on YouTube from people have had done the hard work for you. Provided you watch the model and memory there's not too many problems in using someone elses modded bios.