What an interesting question. At first I was going to say put the FEL on the 2010....that will cost the least, and will give the 2010 something to do in retirement!

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But of course good as those 2010's are, the new tractors should be more comfortable to use. They had better be for the money. But the 2010 is tough competition.
So after thinking about it realistically for awhile I think that if it were my problem I'd consider putting the FEL on whichever tractor has the most convenient transmission for use with that 4n1 bucket. And that's probably a HST tranny. I didn't believe in HST for years, but they are pretty well worked out now. Especially the ones with cruise control - that kinda defeated my last argument against them.
I hope you get the optional Skid Steer QA (SSQA) instead of the JD propriatory type quick attach for bucket to the loader. The SSQA opens up a whole world of loader-mounted implements, and the 3rd valve even more. Last I checked, the SSQA cost more than JD's version, but they have probably fixed that by now.
rScotty