You have very good taste. I know and like both bikes. I would find it very hard to choose between them myself. Luckily, both are outside my usual commute bike budget. That wasn't so helpful, was it. Maybe this would help: if the Sirrus were available in red, in your frame size... I'd call that pretty cool beans. Size is tricky. There is overlap. 5'6" (female?) isn't that small... what is someone 5' or even shorter supposed to do? Truth be told, you could probably fit a medium very well on either bike. I'm not saying the LBS guys are anything less than true children of God but they are all flesh in the end. If you had a bunch of small framed bikes in the back that weren't going out the door fast enough... ...

H