My guess is that the shifters and other components are largely responsible for the difference in price between the two models. Also one has a "triple" crankset (3 gears up font, 8 in the rear) and the other is a "double" (2 gears up front, 9 in the rear). More speeds isn't necessarily better. Some people find that doubles shift more reliably and have less chain rub than triples. If you live in a really hilly area, you may prefer a triple though.

There's no reason why the shifters from the first bike wouldn't fit on the 2nd (or vice versa) but it's not an even trade if you know what I mean.

They both seem like good bikes. I'm not crazy about the aluminum forks, some can lead to a rough ride, others are better designed. Test ride the bikes on a moderately rough surface to make sure that feel comfortable enough.

As far as price goes, since these bikes are sold through a shop you probably won't find much variation in price. Sometimes if you can hold off until Fall, - well after school starts, bikes will go on sale.