Craigslist bikes can be great but a lot of the guys who are fond of them also have a decent selection of tools and a grab box of old parts that might or might not work as a replacement if something needs to be changed. That can really help keep the price of Craigslist bikes down. If you end up having to rely on your LBS to do a lot of work on the Craigslist bike your savings can evaporate pretty quickly. Buying used is also difficult for a newcomer as defects and damage may not be readily apparent to you like they are to somebody who glances at a bike and immediately notices a bent fork.
I don't really see any advantage with the Allant over the Fx 7.2. I think your LBS gives good advice here and the Fx series is plenty popular on this forum. The Allant is a bit more stylish. If that's your cup of tea go for it.
If you do go used put some effort into finding a bike that fits you right. No price is right on a bike that doesn't fit.