Touring - Hub question-why do people recommend Deore XT?

In researching touring wheels I have found many people/shops advocating the DeoreXT hubs and almost no one mentions 105 or Ultegra Hubs. Why is this? Are the Deore Hubs stronger? more reliable?
Thanks

The short answer is that Deore XT is better for loaded touring, while 105 and Ultegra are race-oriented. This is based on research I have been doing recently, not personal experience; I am shopping for my first touring bike now. Edited to add: I have no prejudice here regarding 105/Ultegra vs. XT; I have only used Campagnolo thus far, for riding on the road, not touring.

XT is a mountain bike line of components, so they are durable and can take a beating. They are well regarded as durable, and are pretty cheap.

Part of the reason is that many touring bikes are made with 135mm rear dropout spacing. This is incompatible with rear road hubs like Ultegra and 105 (130mm spacing). Deore XT (and other mountain rear hubs) measure 135mm.

Also The xt's are better sealed than most road hubs and most of Shimano's lower end MTB hubs The Xt's boron heat treated bearing races should last a helluva long time with yearly servicing. and if you are at the ends of the earth You will probaly have slighty better luck finding loose ball bearings than a sealed beaing assembly.

I second that response, I use them on my touring bike and have crossed streams quite offten on my favorite ride. No problema.

Of the 135mm hubs, XT has the best price/performance. If you go to XTR , Shimano start using lightweight materials and sacrifice some durability esp for the axle. The bearings and seals are as good as you can get, parts are widely available and the cup/cone design resists the sideways sway of touring loads better than many cartridge bearing hubs.
The cartridge bearing alternative is something like a Phil Woods which is 3x the price.

Great info- that makes my decision a lot easier- thanks.

I don't agree that at the XTR level $himano starts sacrificing durability. I think XTR rear hubs are the most durable hub known to man, maybe Phil Wood excepted. I have one that's 12 years old I beat to crap on a mountain bike and now use on my commuter with only a bearing change, must have 6,000 miles or more on it easily. The XT is a great cheap hub.