I've never rented from
Budget, but I have rented from Thrifty several times at MCO. The facility is very close to the airport terminal, so the shuttle bus ride is only about 5 minutes and not difficult at all. I always check Thrifty first because they often have much lower rates than the on-site agencies.
That being said, however, I have always been willing to spend an extra $20-$30 to rent on-site. If the rates are only $17 apart, I would go with the on-site agency. The time you save could be as little as 15 minutes or as much as 40, depending on how long you would have to wait for the Thrifty bus and how many passengers have to load and unload; the trip is only 5 minutes, but loading and unloading the bus can take 10 minutes, and you might also have to wait for the bus for 15 minutes.
I travel solo, so if you're travelling with a family of 5 (with luggage), you'll appreciate not only the time savings, but the ease of getting your car right at the terminal instead of having to add the extra shuttle ride in.
So go with Budget. And as KodakFigment said, keep checking the rates at all of the major agencies, because they bounce up and down like a yo-yo and you can often get a much better rate if you check on a regular basis, sometimes with the same agency, sometimes with another agency.
My first ressie for my next trip was with Thrifty - I got a mid-size for 10 days for $204.04; all the other agencies were $40-$100 more expensive. But a few weeks later the
Alamo rates dropped and I got a mid-size from Alamo for $205.65. Believe me, renting on-site is definitely worth an extra $1.61!
Since then the rate has dropped twice; I rebooked once at $201.04 and a second time at $198.98. Sure, I'm only whittling my rate down about a buck at a time, but with 3 months left till my trip, if I keep whittling the rate down a little at a time when the better rates come along, I might wind up with a rate that's $20 or $30 cheaper than my original Thrifty rate - that's dinner at WDW one night on my trip, or covers the cost of the gas I will use in the car.
NOTE: The rates I'm listing here are with the dicount and a coupon I get as a member of
Sams Club. BJs and Costco have similar programs - be sure to check them if you are a member of any of these clubs.