Hi Barry, hope all is good up your neck of the woods.
Hard Floors & Leather can both be extremely profitable, more than carpets usually (unless of course protection is involved). Havent been getting so much hard floors lately, but not too fussed tbh. Funnily enough did a leather re-dye a few days ago for 2 low back sofas - took 2hrs @ £360.00. Product costs were nil as i had a load of dye left over from a job that never came about.
I agree with Derek in terms of ROI not much difference at my end too, but leather just takes longer to get to grips with and a good eye (if your going to do restoration).
Its good to diversify, not only for increased profits initially but to gain more work from the referrals for all the other services you offer.
Cheers
Kev