I'll preface this statement by saying I haven't seen your 2 bike options physically. Having said that I don't see these 2 bikes as a very good test to judge your lbs by. The Giant is a no brainer better as a commuter imho. This guy might be a moron or a genius and tell you that is the better bike. That doesn't mean the Sirrus isn't a good bike (it probably is) just that the Giant seems like an obvious choice to me for a commuter. Imagine if you were a recreational rider the Sirrus would be the obvious (but maybe not the right choice for various reasons) over the Giant.I would echo what others are saying get a disc brake bike to start with or at least one that has mounting brackets and wheelset. It sounds like you have expanded your budget enough for that. Good luck in your search. I think I get why you are talking a while for this bike. for me it would be a big purchase and I would want to get something really good out of it.