Is there any difference, with respect to chain line, between an XT M770 set up as dual ring and a standard dual ring M665 SLX cranks. I am wondering if since the SLX is designed as a dual ring it has different spacings of the chain rings than the XT. I notice that shimano calls out for both to use the 2.5mm spacer on the drive side for 73mm BB. I would think that a crank designed for dual ring operation would have different chain ring locations than one designed for 3 rings to better position the chain line. When using XT as dual ring should I add any extra spacers on drive side to push the chain line out a bit to better center the 2 rings in the chain line?

Why do I care? I have a set of both SLX and XT cranks and am building up a new bike and want to run it as dual ring. Would I be better using the SLX or the XT. If both are mechanically the same I will use the XT.

Hope this all makes sense.

Thanks for any feedback