Hi Andy!
I have found the basic Deore hubs to work very well for the money. That said, the general buzz among world tourists is XT is *not* worth the cost increment in its current iteration, and is found to be shorter-lived in touring applications, according to the Weraldfietser Dutch adventure-cycling forum. LX seems to be the default of choice, perceived as having smoother bearings than basic Deore, yet much longer life in touring use than
recent XT or XTR (older XT was more durable, has since changed with smaller bearings and different races and perhaps axle). Marten Gerritsen, who I respect highly, also recommends LX for touring.
I know this seems counterintuitive...after all, XT/XTR is designed for racing and such, and must be better sealed with closer tolerances, etc.
I haven't owned the higher grades of Shimano for a good while now, so things may have changed; in my own past experience 600 outlasted Dura-Ace by a good margin, and I was a maintenance obsessive (to adapt one of Andre's phrases) at the time. What happened was, the bearings on all cones and such were surface-hardened after initial grinding. On the higher grades, the hardened surfaces were then re-ground to higher standards. Unfortunately, if the re-grinding lapped through the hardening...you ended up buying hubs with cones already nearly worn-out -- the ball-bearings soon dug grooves in the softer parent metal. Perhaps that's what's going on now, but I would have to brinnell-emboss test a current set of cones to see. There have been allegations of hard-anodized aluminum races in the recent XT/XTR line, but I have not confirmed this. It would be a reasonable approach to saving weight for racing, and would account for the shorter lifespan.
My suggestion? If you want to save some money and achieve high value, go with basic Deore. If you want a higher level of finish and (initially) smoother bearings, go with LX (I have examined both under a 30x loupe. The cup races aren't much different, but the cones are. Or, you could do a cone transplant and get much of the LX value in a Deore hub). If you race, XT/XTR will be fine with frequent servicing (which includes replacing the ball bearings and the cones more frequently); just not the best-suited for the delayed-maintenance and heavy loads of world and Adventure touring. I think a Shimano LX hub/Rigida Sputnik rim combo would build up into a very nice, reliable touring wheel without a lot of extra weight. People's needs vary, though. Remember, I'm easy on equipment and used to do all my loaded touring on Mavic MA-2s with 36 15g spokes with 700x32C road slicks and never, ever had a problem with 25kg loads off-road, on gravel, and among rocks the size of shoeboxes. In contrast, the Nomad's Rigida Andras and 26x2.0 Schwalbe Duremes make me feel invincible, as if I am driving a tank or at least a Hummer.
There is also a difference in ball bearings. Shimano's MTB hubs tend toward stainless-steel bearings (rust-resistant, but tend to work-harden), while their road groups use chrome-plated steel balls. Dunno what they use for cup races, but I presume hardened, high-carbon steel. Current XT may use hardened alu and definitely have switched to fewer and smaller bearings.
With all that said, some people swear by XT for touring. See:
http://travellingtwo.com/resources/which-hubs-to-use-for-bike-touringWhat really kills cup-and-cone bearings is poor adjustment. People often adjust-out the play with them off the bike, then squash the bearings when they tighten the q/r. Alternatively, if the bearing play is left too loose, wear is not evenly distributed around the cones leading to excessively high rates of wear. The cones will always wear out first due their smaller surface area, but this same wear will eventually show up in the cups, too. Cones are (sometimes) replaceable. Cups...not so much, at least since Campagnolo's original Nuovo Record freewheel hubs left the market. I still remember replacing a set of cup races after tens of thousands of miles; it was a bear of a job to remove the old ones and set the new ones square in the hub shell.
As for me, if I had the money and was building a pair of high-zoot wheels I planned to keep awhile, I would go if possible for shielded ("sealed") cartridge bearings that are user-replaceable. Phil Wood stuff is very good in this regard, and can be made
completely as-new with only a bearing replacement, which can be done roadside with a 5mm allen and their FSA (Field-Serviceable Axle). Keep in mind the hub bearings can be readily replaced, but there have been reports of freehub pawl failure, a problem quite apart from bearing longevity.
Best,
Dan.
