My LBS advocates Deore componets for a Salsa Fargo frame build up. I was thinking about SLX components. What would be the notiecable differences between the two builds?

Availability of Dynasys is a big one, and it only matters if your using Dynasys shifters, which SLX comes in both Dynasys and non Dynasys. If your not, go with Deore. It only weighs a little more, costs a little less, and lasts maybe 5 miles less then the SLX. Other than that, nothing really that I'm aware of. I'm running Deore myself.

PS: this is Deore and not Deore XT, correct?

As mentioned above, the high end groups normally offer one or two of the latest features, and offer the lowest weight. Mid range groups are a few grams heavier, but usually perform as well or better, and may be more durable in the real world where bikes fall over, get bumped, etc. entry level stuff is often stamped steel instead of forged aluminum and bearings are another place they cut corners. I normally buy last years midrange "pulls" for about 25% of the price for this years equivalent. I leave the high end matching gruppos to rich folks who care about such things.

Thanks to all for the replies. I am going with Deore.

I'm finding that Deore rear derailleurs wear out their bushings and get sloppy a lot faster than they used to.

Nine speed or ten?

FWIW, I like the look of the SLX cranks much better than then the Deore ones. I run the SLX double right now on my own Fargo. (However, I am planning a switch to the newer, 10-speed XT 26/38 double in order to get more top-end gearing).

IMHO, you want a Shadow derailleur. Are those available in the Deore line? I do not even look at non-Shadow models anymore. I hate the cable loops on those, and the springs are stronger on the Shadows.

Otherwise you are generally looking at less weight with SLX, and a little better fit and finish.

That's why I've been partial to Sram, that and the shifting efficiency. However, on one bike I run an XT Shadow rear rerailleur and find it as good as the Sram X9 on another bike. I also prefer the Shimano shifter that came with the Shadow (push or pull to upshift vs. push for Sram or pull for standard Shimano shifters).

Have you considered Sram X7 instead of Deore?

I have a Deore Shadow (not XT) on one bike and I like it a lot, very crisp shifting and no cable loop. Other than that I've been using regular Deore parts for many years and had very little issues. Even if something breaks or wears out it's easier to replace a $60 RD than a $200 one. The only exception is the latest XT front derailleur: angled adjustments screws, makes it very easy to work with it.

However, I've been hearing lots of good stuff about SRAM and my next full build may as well be based on SRAM. I'd like to try Matchmakers with Avid hydraulic brakes.

i have a deore crank on my LHT and find it more than adequate for everything. I've never had problems with deore derailleurs either.

I've had a lot of trouble with deore hubs coming out of adjustment, and switched to cartridge bearing SRAM hubs for great success.