These are both aluminum-framed roadsters and the main difference is in the component spec. With the 1500 you're getting better "bits".
Far more important is that the bike fit you. You say you're "new" to biking; before I'd plunk down the money for any used machine I'd take an experience rider along to check out the bike mechanically and to see if it's possible to adjust it for a good position on the bike.

You may be getting a bargain; these are pretty much in the "entry-level" of road bikes, and a lot of folks will buy a machine like this, ride it for a year, and then want to move up. You may be getting a lightly-used bike with lots of service life.