crank arm length on my road bike vs xc mtb

hi all,

just after some advice and opinions please.

i race xc and my current mtb set-up has a 175mm crank arm. i've just bought a new road bike for training (i will also prob race it) and it has a 172.5mm crank. my thoughts are that although if i were purely riding and racing road then i'd probably change the road bike to a 170mm crank. given the situation i'm in and the types of riding i do, i was thinking the crank on my road bike would be ok as it'll mean less of a 'jump' in terms of transferring between my road and mtb. from a performance and potentially injury potential issue do you guys think this is correct?

i'm 5'7'' by the way.

many thanks in advance.

note to mods: i've posted this also in the mtb forums section thinking both 'sides' may have good advice to offer. sorrfor the duplicate post.