I don't have either but i would go with 35L because 24mm would be too wide on a FF for my taste.
IMO, you can simply backup from your subject a little to get the 24mm focal range and it is also closer towards 50mm "normal" focal range.
I've tried zoom Sigma 17-50mm 2.8 on 7D and at 17mm on 1.6 crop, it is equivalent to 27.2mm on FF.
and i felt that 27mm is plenty wide and mainly shot zooming in, thus closer to 35mm focal range.




