Better also factor in new brakes - the Avid SD3's bite* what's unholy. Those are stock on both bicycles. I speak from experience when I say the frame of the 7.3 FX is a excellent one. I have no experience in the GFM's "gold" aluminum. The Trek 7.3 would lend itself to future upgrades perfectly. I think you know which one I'd get - a proven winner.
* The SD3 brakes are only available as stock components - they are not sold individually. They go out of adjustment by simply looking at them. All the time. They were the first component I swapped out on my 7.5 FX. They drove me knutZ! But they did stop you.