More than two years after SRAM brought the 12-speed Eagle to consumers, Shimano finally has a competing drivetrain.
The new Shimano XTR drivetrain has a 10-51 tooth cassette though, whereas SRAM’s Eagle is based on a 10-50 tooth cassette. So who beat who?

Crank set
Shimano’s new XTR M9100 crankset weighs a claimed 511g, in a 175mm crank length. It’s available in a 162mm or 168mm Q-factor, and a single chain ring can be directly mounted. For mountain bikers who want even more range, a double chain ring option is available with the new XTR also.

Derailleur
The derailleur sports improved chain retention and weighs 237g. It will come in three different options, all with a larger 13-tooth pulley to reduce friction, and will accommodate all 1×11, 1×12, and 2×12 setups.

Cassette
Shimano’s new XTR cassette is a combination of alloy, titanium, and steel, all in an effort to make it lighter. With Hyperglide+, Shimano is aiming for smoother shifts, up and down the cassette. Shimano claims that this revision of Hyperglide will allow it to shift 30% faster. The cassette will be available in two different options: a 359g, 10-51 version and a 349g, 10-45 version.
Shifter
The XTR shifter gets an update as well. Shimano says the new shifter is more ergonomical and needs 35% less force to shift. It weighs 74g.

Brakes
Shimano updated its XTR stoppers too. They introduced an “enduro-specific,” model. This is of course heavier than their cross-country race targeted model. The BL-M9120 and BR-M9120 boast a 4-piston caliper that Shimano says has the same power rating as their downhill-oriented Saint model.

The M9100 brake is 26g lighter than the previous edition Shimano M9000 brake, and will still rely on a 2-piston design to keep them lighter for XC folks.
Other Highlights
Shimano announced their first dropper post lever that is compatible with most major dropper post brands. They updated their XTR pedals, hubs, freehub, chain, and brake rotors.

In terms of pricing, a 12-speed cassette is $380, a single-ring crankset is $420, the rear derailleur is $260, a shifter is $130, a chain ring is $130, and a chain is $65. For the new drivetrain you’ll pay a grand total of around $1,385, give or take.
Shimano says that the new XTR components will be available for consumers sometime in the fall.
Yes. The new freehub body is not compatible.
Coming into the market so late, you would think Shimano would have marketed the new drivetrain at a much lower price point. It’s going to be interesting to see if they can effectively break into this market. I’m guessing they are going to have to give bike makers a pretty sweet deal on new models to take away business from SRAM. You would think that they’ll have to out compete SRAM somewhere/somehow to break into the market.
I guess they are not competing with GX Eagle this year.
“who beat whom.”
#grammarPolice
resuming the head to head competition with the 2 big boy OEMs (& the multitudes of after market options) will benefit every 1X luver (never SRAM folks, never Shimano folks & riders like me w/ SRAM drivetrain, Shimano brakes) on the price points & future refinements.