So far have been in 6A, 7A, and 17A - 17A easily has the most legroom but gets extremely cold due to the exit door (and sometimes has condensation dripping from it). For me I would prefer 6A, then the rest of premium windows (I always go left side because I fly into/out of SFO a lot), then 17A/F, then 16A/F. All my flights are transcons between BOS and SFO.