Prime lens.

And just go for the m4/3 (OM-D/GH3?). Benchmark or not, I'll love to see these L-series zooms match the 75mmF1.8 in the sharpness department. I find it hard to believe they even come close.

I know people who went from 5DII with L-series lenses to 4/3 (and that was even the E3), because they wanted the Zuiko 150mmF2 and the Zuiko 35-100 for better sharpness. Having shot with E5 and beautiful lenses, I can assure you the m4/3 system isn't lagging behind on sharpness. Olympus primes like 45mmF1.8 and the 75mmF1.8 offer superb sharpness.

I bit the bullet and went from E5/12-60/50-200/500F2 to OM-D and lenses, and so far there's nothing to regret.