I am certainly not going to say that warranty on the frame isn't important as I have read enough threads about owners who discover some kind of manufacturer's defect and had the frame replaced. However, five years is a long time, and a lot of miles and stress can be put on the frame during that time. If there is a manufacture defect you would have discovered it by then. The point is, five years is a long time, and if you're going to be all in on this chances are that you'll have moved on from the Cube in five years into something better, maybe a carbon frame, electronic shifting, custom frame, etc.

Having said all this, if you are still unsure about buying a less-known brand, at least in North America, then go with the Cannondale. You'll sleep better at night.