From experiance I recomend that you go with a 12 inch deisel. They can handle the wide crotch anlges better, even if you are splitting everything over nine inches. I've used a wide range and anything under 12in you have to work too hard to get it to work well. and your talking only 8 or nine grand more. It will effect the Mhrs enough to make it worth while.
The deilsel because the are less prone to lugging and stalling. Better power at lower rpm. I tried the 85hp 13in morbark, oo la la.
It's nice to be at a rich golf course! I'll gloat to yall in Nov. as to what I buy. (chipper, lift, splitter....)