Sufficient graphics memory for new iMac and Lightroom or Aperature

[olyduck]

I'm  looking at the new iMacs, but am concerned about the cost of getting one w/dedicated graphics.  I am not a gamer, but I want to retain capability to use Lightroom or Aperture, and do light video editing, without the machine slowing to a crawl. 
1/ Would the 256 ATI dedicated graphics be enough?
2/ I heard somewhere that NVIDIA may be superior for video editing. Since iMac dedicated graphics are only ATI, would that be a compelling enough reason to reconsider a Windows & machine?

Thanks, Dave

[KeithB]

Get the best graphics you can.  Here is an Aperture discussion about it on the Apple boards.  You can join there and ask your specific question, too.

http://discussions.apple.com/thread.jspa?threadID=2238143&tstart=150