I had the chance to switch sleds with lightning800 on the last trip and all i have to say is WOW the 2010 front and rear suspension is sweet! after the upgrades I did, mine it's 100% better than a 09, but the 2010 is still easier to pull over and stay over than mine after my upgrades . the conditions were about 6inch to 1 ft on top of setup snow.
IMO I can't say that the 2010 rear suspension is better than the holz but if I had of known the 2010 kit was going to perform as well as it is, I would of spent the money on the upgrade kit.
I found out that the 2010 lower a-arms are different than the 09, increasing the castor to make the sled softer in the front end, my dealer was telling me that they found this out when a customer damaged his e-module and a-arm, but had a 09 arm installed to complete his trip, after the e-module was repaired the sled had 1 ski further forward than the otherone and had to get a 2010 arm to replace the 09 arm on the sled.