Personally, i think you should look at the individual components as oppose to looking at the group (or brand), and i think that should go for all components. But as for the drivetrain...
Crankset: XTR M970 - Ultra stiff, ultra light, superior shifting performance. Don't be deceived by it's lightness as most people associate this with having compromised strength. It in fact uses higher grade aluminum (duralumin or 2000 series aluminum) to achieve increased strength but lowering weight. This series of aluminum is second strongest to 7000 series, which is what Thomson stems use.
Front derailleur: XTR M970 just to go with the crankset. But i'm not sure if there's much discrepancy between an XTR and XT FD, so i probably wouldn't notice the difference.
Rear derailleur: XT M772 shadow - because i don't trust the carbon cage on the XTR and at the time of deciding which to get, apparently the XTR shadow had some manufacturing faults.
Cassette: SRAM PG-990 - i like the red bits
, but seriously, it's SRAM's flagship cassette and the XTR is much too expensive.
Shifters: XTR M970 - Shifting features, such as double release shift, instant shift when you press the trigger (as in you don't have to press and release, it shifts as soon as you press), use thumb or finger for the trigger, buttery feel, ergonomics. Why not SRAM? I prefer the 2:1 ratio because it (inherently) allows me to shift gears with less stroke of the paddle, so i find that i can shift faster. Likewise, SRAM only 'inherently' has less margin for error in shifting because of it's 1:1 ratio, but if you tune your shimano stuff right, you will also achieve accurate shifting. I also don't like the ergonomics of the SRAM shifters.
Chain: Not sure, i go with SRAM for some unknown reason.
But anyways, this is me of course. Everyone is different.
