I;d say buy the $500 1.2 and see what you think.
Huge benefits: the price is right, the bike is new, and it is high enough in quality that you'd get to fully experience owning and riding a road bike for a decent price. Likely the $1200 bike you'd buy, this year's model, wouldn't be much different than the older Trek 1.2, and would cost more than twice as much. Then, if you decided you wanted a different style of bike, or wanted to do a serious upgrade because you loved,road riding so much, you'd be out all that extra money and have no added value form the bike, which would still sell as an entry-level used bike.
It looks like the 2016 1.2 has Sora 9-speed, which is good value (
https://archive.trekbikes.com/us/en/...ompact/details) with an Al frame and CF fork--exactly what you'd wan't and probably what you'd get for most new entry-level bikes.
Buy the Trek (IF it fits) and then see how much you actually ride, how much you like riding, how long, where, and how often you ride. if the Trek suits you, it should suffice for years. if you decide you don't ride enough, or want to do more rail trails, or want a more relaxed frame, or want a more expensive bike, or whatever, the 1.2 would still have been an excellent investment and would be an excellent back-up bike.
Of course, fit is first and foremost. So, if you don't get the Trek 1.2, ride a Bunch of other bikes and see what you like. Sometimes a shop will try to fit a rider to the bike the shop wants to sell .... so sit on a Bunch of bikes and find out what's comfortable for you.