I think Penske is the best. Buy it directly from Penske though. Contact Shane Sweigert or Cole Sietzinger at (610) 375-6180. Those guys are the best. By buying directly from Penske, you cut out all of the middle men and get to deal with the person/company that is actually building the shock.
All Penske shocks come from Penske no matter motorcycle suspension shop you deal with. When you buy a shock from a suspension shop, they have to pick up the phone and order it from Penske. Things get lost in translation. Deal directly with the factory.
See my post titled "Kudos to Penske" in Tuning and Handling if you want to see how Penske treats their customers and the hassles you go through when dealing with a middle man.