Nice simple one whats the diferance between the LX M570 and the M580 I want a 31.8 clamp top pull front mech i can see that the M580 is a multifit like my old Deore with a set of shims and can be used top and bottom pull But the M570 is a dedicated fit size and is availible in Blue and gray which will match my full LX drive train. So which should i plump for?