The Trek has a very slack head angle, nice for cruising but feels a bit strange after more responsive rides. In terms of value, I picked up one for free at a music festival, the owner had rode it until the tire shredded into oblivion then rode on the rim, lucky it was on grass.
The Giant is also a good bike, I have an ATX840 I scored for a 6 pack. Would be much more exciting to ride than the Trek if it's a bit twisty and bumpy. I can still stay in the top 10% of descent times on fast single track on mine, as long as there's no big jumps.
If it's reasonably flat road then I'd be going for the Trek for commuting, the 700c wheels will roll better than the 26" on the Giant. If you have a few big hills you can put one of the Mega Gear Freewheels on it for about $15, the derailleur can cope with a 34T.
The brake blocks on the Trek have probably gone hard, happens to a lot of old bikes, ozone makes the rubber set like concrete. Change them out for a set of modern ones with swappable pads for about $7 a pair for something like Clarkes, then you can put Koolstop Salmon pads on in the winter. I did that on mine and they work fine.