Horseshoe Meadows would be the easiest. 3-4 days I think is what I hear (never managed to do it from this direction yet).
If you're really a masochist, you can do Langley on the way as well.
From Onion valley it's 5-7 days. Forester Pass is a long slog up (day 2 usually), but after that only the Whitney climb is going to kill you.
Edit: Messed up the passes. Forester is the 13k slog (your results may vary).
