Originally Posted by 1xGuy

Agree with this - OP, your shifting performance will only be degraded by a non-system cassette. For me, I would first consider laying out for the XTR cassette - but they are very expensive and hard to find, and the weight savings vs the cost is hard to justify. But you will save weight and shifting won't suffer. A possibility - and I am only spitballing here - if you race and are looking for the lightest bike on a particular day, get the Garbaruk and put it on for races, falling back to the XT when not racing. I would designate a separate chain for that setup, and you may also need a new driver body (not sure which it uses), so that would be part of the added cost - likely approaching XTR cost. Full disclosure: I have not done this, and have no idea how well it would work, but could be passable for a few hours after proper adjustment - the flipside to that though is that having a mechanical issue during a race is a big bummer. Wheels and tires is where I would look first though, if you haven't already done it.