MBP 13" vs. MBA 13" in closed clamshell mode

[balcon2]

It seems that the benchmarks on the rMBP and MBA 13" machines are pretty similar. But the rMBP processor is significantly more powerful. I am guessing that the similarity in bechmarks is due to a lot of the rMBP processing power being used to drive the retina screen. If that is the case, would one expect that the rMBP would give significantly better performance in closed clamshell mode, driving an external 24" monitor and doing graphics tasks? This is relevant to me, since most of the time my laptop will be used in closed clamshell mode and I do a decent amount of work with Photoshop and InDesign, and also work with a lot of windows open simultaneously. Thanks for anyone who has some knowledge of this.