For 2005 models, a side by side comparison component spec would say the Scott Aspen is a superior bike. That reflects in the price also, as it is 25-30% more than the GT.
As far as ride quality, handling and frame strength, well, they are fairly similar in geometry, tubing material, etc. So, I would anticipate the frames themselves being essentially equal.
The fork on the Scott is marginally better than the GT (Manitou vs. SR).
Probably the most important issue is Scott is a company that is coming on strong, while GT is (sadly) slipping into mediocrity. If you should have a frame warranty issue, Scott would likely be a faster and less complex responder.