I think that Trek is a great buy, assuming it's all there. I like old Schwinns, and rode a Continental for years, but that doesn't hold a candle to the Trek IMO.
If the size is right, and if you're willing to tackle the project, go for the Trek. A bike of this vintage most likely needs all the bearings repacked and all the cables & housings replaced. Tires and brake pads are suspect, chain could be shot. You could spend over the asking price in parts alone. OTOH it might not need any of that. Either way, it's worth $80.