I personally would run, not walk away from the "big dog" vs a Gravely lol.......if those are you only 2 choices. Gravely has proven they make good equip and stand behind it and you see a lot of commercial guys using them with little if any issues.
IMHO a Diesel is overkill for only 1.5 acres.....and while Kubotas are nice machines, everything I have ever heard was they are $$$$$ to maintain as every part for them is very expensive.
So I would go Gravely, or Ferris (is2000?), but from what you posted Ferris was not a final option? They have the best ride.
Also look into joining an Equine associtaion - I keep hearing that you get a nice discount if you are a member of like the AQHA - it's $40 for 1 year. Discounts can be into hundreds of $? Ask your dealers about it.....