That's probably a question better answered by your accountant but I'll give you my thoughts on the subject.
Finantial advisors like to say "never buy a depreciating asset and never rent an appreciating asset." This simply means if it's going to decrease (like equipment) in value rent it or lease it. If it's going to increase in value with time (like property) you should own it.
This is especially true in business because there are some tax benefits with leasing. You'll need to ask your accountant but leasing really begins to make sense when they put the dollars and cents down on paper.
I have noticed on e-bay that exmark seems to have great resale value. I havent really noticed it with other brands though. It may partly be an ebay "caught in the moment bidding war" thing, but thats what I have noticed.