I love vintage steel bikes and own many, in fact my daily commuting bike is close to 50 years old. That said I recommend you buy the newer one if it fits you! It's an excellent price and you will be quite happy with it.
The vintage Trek may be a nice bike, but you really need to be extra cautious about those advertised on CL, etc. It's not uncommon for sellers to misrepresent condition, whether intentionally or not, and almost always ask way to much. If you really like the idea of a vintage bike, have someone knowledgeable help you look it over. It will likely need something, despite being advertised as "excellent". And what in the heck does "well-stored" mean? If it's been sitting around for a long time, it will need a thorough going over. If you are up for this addictive hobby, great. Otherwise, buy the new one and once you get into riding you can then diversify.