If you want the best sound, KSC-35, no question.
I like the sound better than the PP's, especially with the center-hole mod.
Some people seem to favor the KSC-75 in terms of comfort. Personally, the 35's are more comfortable, lighter in weight, and not as goofy/alien looking as the 75's. The 75's can be a bit cumbersome whereas I often forget that the 35's are even on after a few minutes.
The bottom line though, judging from your request, is that the sound of the 75's just doesn't compare to the KSC-35's. Other people seem to think they sound very similar, but I'm confident that if someone with discriminating taste were to use both regularly, the sonic differences between the two would become more and more obvious.
I don't think you can get portables any closer to the full-size Grado sound than 35's.