From a different perspective: You say you have four acres and all the landscaping is done. Four acres of landscaping is one heck of a lot of landscaping so is it safe to assume there is some measure of your property that is still not landscaped? What are your plans for that section, is that where all the grass is? Any plans to expand the compound? Build? Level? Trim? All jobs for a small tractor.
I have three acres of landscaping on a 10 acre plot. The wife is into gardening of all types, president of the local garden club, all that. One thing I know about most large gardens - and I don't know about yours - but for people who like gardening and landscaping, the job is never done. Plants and trees are always dying, being planted into wrong locations, over-growing, under growing, plots and beds are ripped up and evolving. A true garden is a thing of constant change. Very few people keep the garden status quo. My B21 is the best thing I ever bought since it is small and gets into tight, already-landscaped, spaces. It is strong for hauling DG/compost/logs/landscape rocks - all thanks to the FEL.
You might consider resale value too. Small tractors usually sell the first day on Craigslist, ask anyone who has tried to hunt a good, used one down.