MY co-worker recently went through the same comparison. After looking at a few bikes he quickly gravitated to the 7.2/3 FX series. His wife was not supportive of buying a quality bike, and through that a Wallmart bike would be fine. Thankfully it didn't take much to convincing my co-worker that buying a sub $200 bike that ha to be self assembled (or reassembled because there is a good chance it wasn't done right) and will probably fall appart soon.
After looking over both bikes very carefully I'd have to say that the tires, the crank, and the derailer upgrades are worth the extra $150. I've had the Invert tires and realy did not like them. They buzzed a but, and picked up loads of road grit. When the tires got older they would flat out all the time as all the road grit just sat then getting pushed in deeper and deeper with every turn. I already had the 25mm verion of the Race Lites on my road bike and was pleased. I now have the 32 mm Race Lites on my hybrid and am SO much happier. My Gary Fisher also has the Deore rear derailer, and it works very well. It survived it first year round commuting in Buffalo (NY), and still shifts spot on. There are higher grade derailers available, but the Deore is an excellent unit. As far as the difference in two versions of the frame, I don't know if anyone could feel that to easily. The 7.3 gets you out of the bodum rung of the parts bin and definitely offers a bike that if maintained could go for many years of troublefree use.
Happy riding,
André