There was a point in upgrading when the steel hunks of Shimano used to rust and look bad. But with the new Shimano ones being light and functional I don't see the point anymore. When the plastic bits of my crossmax's finaly fell off I bought a set of DT swiss QR's second hand - seem to hold the wheels on fine and were cheaper than XT's (just). I'd go for Shimano's unless I wanted pimpy - in which case the Salsa's would be my "retro-cool-back-in-the-day-rasta" choice.
This forum's been done before, have a search for it.
I'd second almost everyone else, go for the XT.
Also, my LBS suggested to me titanium skewers wouldn't be as rigid between your dropouts as steel, so tracking wouldn't be as good. Down to the emphasis of the build obviously, since titanium should be more rigid, but not if they've gone too light.
Here is the relevant detail: Hope Mini #3s (185 front, 165 rear) Forx RL Stumpjumper frame
The braking power was too much for those skewers, even if I used my foot (!) to stamp down the skewer. They don't dig itno the metal like a normal skewer, hence much slipping.
I have now changed to Salsa and I only touch them when I change tyres. That's a gripping report...