These guys are right, we are a biased group because we all love our tractors. It's nice to be able to do a project when time permits and not have to schedule it on a certain day. A couple years ago I rented a tractor to do some grading in the back yard. I had to pay a deposit to reserve the tractor ahead of time and schedule it around my work schedule. Well the day came to do the work and it POURED down rain. I can tolerate working in the rain but the ground was so muddy the tractor was ineffective. I got my eight hours of running time out of it, but didn't accomplish much. Now that I have my own machine, I don't have to worry about availability or weather. I can work an hour here or there, whenever I want to. Since I got my tractor used and got a good deal, unless I break it in half it will always be worth close to what I paid for it. Fuel and maintenance costs for the first 150 hours have been minimal, and best of all owning and operating a tractor is fun and a great stress reliever.
If you just have a few specific jobs to do, I feel you will save money buy hiring the work done, unless you are an experienced operator. The "learning curve" when you rent eats up a substantial amount of your rental time. If you get your own tractor, you will learn as you go, and you will be amazed at the tasks that come up for your tractor. But, like I said before, I am a little biased.