Test ride each of them and then decide. The equipment on one or the other might be slightly better but they're going to be in the same ballpark.

If you hunt around you might be able to find something on closeout or a demo model with Tiagra shifters. Soras work fine but it's impossible for most people to shift them from the drops as has already been mentioned. Maybe not a big deal to you now but if you start to get really serious about road biking, you'll eventually want different shifters.

You can start out with the Soras of course and upgrade later but having new shifters installed is not cheap. If you get comfortable doing the mechanical work yourself and keep an eye out for good deals you can do it without paying an arm and a leg.