Wow! That will be a really nicely equipped bike ... AND, you must have really deep pockets!
FYI. The difference in the rear derailleurs is that the 970 & 971 are the older/traditional, slant parallelogram rear derailleurs -- the 970 is the RAPID RISE version & the 971 is the one whose "pull" is the same as on a ROAD rear derailleur (in the distant past, the RAPID RISE variant had the "odd" number in the sequence).
The 972 is the SHADOW version -- RAPID RISE.
While the 972 rear derailleur looks really nice (exquisite, IMO), you may really want to consider equipping your bike with XT components ... it is still my prediction that Shimano will eventually use RAPID RISE type rear derailleurs in their road groups, too, UNLESS they eventually improve their STI shift mechanism ... not that anyone will really care until that particular 'day' arrives!
FWIW. In the past (and, probably now) there was little-or-no functional difference in the Shimano front derailleurs of the same vintage ... that is, you probably woudn't notice any difference on a bike with a LX-or-lower front derailleur if you compared it on a bike with an XT or XTR front derailleur (presuming the same XT/XTR shifters were used) ... and, other than the clamp & cosmetic difference to the outside plate, I would say they are therefore equivalent.
And, depending on the "trails" you ride on, rear deraileurs are sometimes subjected to excessive abuse; so, you may want to consider choosing an XT rear derailleur.
Perhaps, more than with Shimano's ROAD components (i.e., Ultegra vs. Dura Ace), the XT "stuff" is really the best value if you want something better than LX.