2010 Giant TCR Advanced 2 is likely Ultegra (Shimano 6700), since in 2010 there was also a Giant TCR Advanced 3 was 105 (Shimano 5600). The 2011 Giant TCR Advanced 2 is 105 (5700).
If the 2010 Giant TCR Advanced 2 is Ultegra, then I'd take that. If it's 105 (5600) then I'd take the 2011. If both the 2010 and 2011 are 5700, then I'd take which ever was cheaper (if it was significant) and/or which I thought looked cooler.