I actually know WAY more about this topic than I care to. But it's part of my job. And our shop seems to have a big mtb clientele.
I'll just throw out some general things..
(remember we are in the dessert. Loose rocks, sand, sharp rocks, and cacti that jumps out and attacks).

Kenda Nevegals seem to be every magazine editors favorite tire. So we sell them, but we don't particularly like them. We grade them about a B I guess, but we like others better.

We favor the maxxis line. Most popular overall tire is the Ignitor, followed by the advantage. Crossmarks are the tires our racers use.

We also carry the Kenda El Moco, but it wears out very fast, as it has a soft compound. "Sticky" wears quicker than DTC (dual tread compound)

I refer to the kenda small block eight as a hateful tire, as it does not do well in deep sand. I spent a miserable trip in moab riding my womens anthem on the stock small block eights.

We sell some of the wtb line, and the michelin dry xc, but not all that often. Like the nevegals, they are ok but our riders and staff prefer the maxxis line.

Tips about going tubeless....

Little known fact is that both kenda and maxxis (amongst others I'm sure) state that if a tubeless sealant such as Stans or slime pro are used it will void the tire warranty. - Not that anyone let's that stop them. But buyer beware..

Kenda tires, esp the small block eights do not take tubeless conversions well. The sidewalls are thin and the sealant literally seeps through them. W/Kendas you really need to use a tubeless tire.- tho the nevegal is the best of the line we have found so far.
OTOH the maxxis non "LUST" (tubeless) tires seem to take tubelesss conversions well. But it is nice having the thicker sidewalls of the UST or LUST tires. BUT they are more pricey.

We have had some maxxis warranty issues. The tires literally developed a "tumor" when the outer tread started to seperate from the inner casing. Think of it as a big pimple on your tire. But this has always been covered under warranty.

oh and one last thing. The guys do bot like the "exception" tires in the maxxis line. Tho I can't remember why.

OH! And tho I SWEAR by my continental road tires, we have had three sets of mtb tires blow off of rims mid ride. So we don't carry them anymore. Sad cause we LOVE their road tires.