Having owned both (M35A2 and M925A2):
M35 "+": Can burn 100% waste motor oil, removing the fuel cost of the hobby. WildChild467 drives his as his daily driver all summer long, with $0 spent in fuel. Is more of a reasonable size to park in your yard and in public. Has 5 speed manual trans, so it really feels like a truck. These trucks don't get stuck very easily, check some YouTube videos of what they can drag themselves out of, un-assisted. That is what made me buy one to begin with. Engine sound is fabulous with an earlier generation "C" "Whistler" turbo.
M35 "-": Has manual steering, can add on power steering for $2000 or less to alleviate this. Top speed is limited to 50-55mph, unless you add a higher 5th gear in the trans and/or taller tires, which is not cheap to do, and may require a small boost in engine power to reach and maintain top speed. Vehicle is loud at higher RPM, no factory muffler and exhaust pipe exit is in front of cab windshield (looks cool, but loud).
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5T "+": Physical size. Gets a lot of attention at 10' tall and 48" tall tires (if singles). 4mpg if 855 powered, and 10mpg if 8.3 powered. 900 series have power steering and auto trans, making it "easier" to drive. Later ones have auto tire inflation (CTIS), this is fabulous, if working. Checks and fills tires at every engine start, automatically. Factory top speed is about 67mph (8.3 equipped, unsure of 855), so can be driven on freeways and 2 lane roads without making 100 people mad behind you.
5T "-": Physical size. More difficult to park at home and away. Can be done, but need to really be paying attention or park far away in parking lots. Weight of 20,000lbs or so. If you are going off-road, I would recommend to get one with a winch, as this is a lot of vehicle to get stuck and retrieve if need be, would likely take a piece of construction equipment to be brought in to do so, unless another 5T is close by. Even then, sometimes it doesn't work though.
As advised, check license plate fees and insurance for such in your area. These vehicles are large, heavy, and somewhat unique. M35A2 is maybe 12,000lbs. Insurance can be a little tricky, especially if you have any points on your driving record. Sometimes these are classified as commercial vehicles, and sometimes not, state by state dependent. Again, check your local DMV before you bring green metal home.
