They're all all pretty nice. At the same price I'd say sure, go with a bike with Ultegra. For what it's worth Giant just introduced a new policy of replacing or repairing any Giant branded carbon part (including frames) to the original owner for two years no matter what, including racing, so that may be relevant. My experience working with the industry is that Giant and Cervelo are easier to deal with for warranty and for replacement parts (disclaimer: I currently work at a Giant dealer, and previously worked for a shop that sold both Giant and Cervelo, and previously dropped Cannondale because they sucked to deal with. My personal bike however is an older Supersix which I love, so there's that).
Take into account which shop you like working with better. Also take into account what help they'll provide regarding fit and service, to whatever degree that's relevant to you.