Probably the 24-70 II if price is no object, but (and this comes with the disclaimer that I am less experienced than many of the very talented folks here) I personally haven't missed f2.8 in the 24-70 range. For portraits or indoor/outdoor sports I nearly always grab my 70-200 2.8 IS II, occasionally my 50 1.4. I would however miss IS. For landscapes at f8 or narrower, with a polarized filter attached, the IS has been a huge benefit. For my most important shots I will use a tripod, but there are times that I just don't want to lug the extra gear or keep family and friends waiting while I set up and compose. All things being equal, this means that my ISO setting would have to be two stops higher with the 24-70. What I would welcome is the improvement in distortion at 24mm. It's easy enough to correct in post, but you lose a bit of image quality. Since you are renting both you will have a nice opportunity to compare the results. Run them through your most common use cases and see which one meets your needs more often.