Go XT, knowing that this years XT is last years XTR.
That's a bit like saying "Go Camaro, knowing that this years Camaro is last years Corvette." I mean, they both do the ~ same thing and there is definitely a lot of trickle down but the quality of the products is dissimilar. XT is a workhouse groupset - which is high quality but definitely with a focus on value, where XTR, in general, uses much higher quality materials (at a premium price).
If you are planning to run the bike long term and you don't have a history of smashing your gear changer, the one place I would personally consider springing for XTR over XT would be the shifter. The quality difference is notable especially over the long term.
I imagine my next geared bike will be 11spd SLX (when it's released) w/ an XTR Shifter and XT Cassette.
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