In reply to gethin_allen:
Evening! Mr TC here. Afraid I do have a bit of a TCR habit. I've had TCRs of various sorts since they first came out over a decade ago. Of the two bikes you have mentioned, I'd recommend the TCR Composite because of the geometry. Depends a little on what you are used to and how physically flexible you are but you can compensate for any deficiencies in the flexibility department by flipping your stem/keeping a decent stack of spacers etc. The TCR should do everything you could ask of it and it should also be able to take SKS Raceblades (long or standard) if you need to fit guards so long as you run 23mm tyres, so great for winter and commuting.
Downside of the frame is that the top tube (at least on the Advanced SL and the alloy TCR that I run) is quite wide and if your knees are prone to coming in a bit at the top of the pedal cycle, they can hit the tube. That might just be me though!
Other thing worth noting is the sizing. Don't know how tall you are but check all that out carefully. Stating the obvious, I know, but I've found that there is quite a leap between Large and XL for example, especially on components such as the stems that Giant supply, with the stem length and therefore reach stepping up quite significantly. Again this is just my experience.
Other than that, not a lot else to say. Super solid bikes. Not the sexiest and Giants do have a bit of brand image problem because lots of folk on BTW schemes opt for the Defy, because it's such good value for money. Consequently there are oodles of them around. TCRs are a bit rarer and definitely have a bit more of a grin factor. Hope that helps and you get what you want. Enjoy!