I've test ridden both; as it happens, my choice came down to the Rapid 1 or the Sirrus Comp. I went with the latter simply because I found it very slightly more comfortable, and preferred the v-brakes to road calipers.
In my view, both the bikes you mention are excellent -- but they are a little different. The Norcos are slightly more relaxed in their geometry, whereas the Giant Rapid series really is simply a Giant Defy (road bike) with the top tube slightly lengthened (for a given size) better to suit flat bars. Essentially the same frame/frame material. I prefer the Rapid (to the VFR), but that's just me. I also second Talldog's view: Giants are unbeatable re. value for money.