Looks like a solid choice.

Is this one of the models with the hydraulic drive? Then keep in mind that high-pressure hydraulic hoses have generally have to be replaced every 10 years or so.

You should seriously consider fitting a track kit on your RTV, and maybe even the quad. Looking at some videos [1, 2, 3, 4], vehicles with a track kit have much more ground clearance and seem to deal with mud much better than wheels. To my engineering eye, tracks on an RTV look "right". Tracks would lower the ground loading significantly.

Roland --- It means a lot to get your seal of approval! We actually considered the tracks, but they're out of our price range at the moment. Fortunately, it sounds like you can put them on relatively easily after the fact. So, if we save our pennies again....

I still think a tractor with the carry all another poster mentioned on the other thread is the way to go. But new and shiny is nice. I'd still buy a Deere because I am a buy from an American company kind of guy.

Diesel can cause trouble if it gets really cold. Paraffin from the diesel can crystallize (starting at -7 °C) and clog fuel filters and injectors. If there is water (from condensation) in the tank or fuel system it can freeze and cause damage. Not sure about the situation in the US, but here in the Netherlands diesel fuel that is sold in the December to February period contains additives to prevent troubles. If the tank has a drain valve on the bottom, use that regularly to extract some fuel and check it for water or microbial growth.

W.r.t. hydraulics, a lot of the fluids are toxic, especially when ingested or when they enter the bloodstream. Wear appropriate gloves when handling them. You should not go looking for an hydraulic leak with the motor/pump running. A high-pressure jet of hydraulic fluid from a small leak can easily penetrate deep into your flesh. Some hydraulic fluids are hygroscopic, in which case you should keep the tank and containers tightly closed.

If you want to do maintenance on hydraulics yourself, make sure that whatever you're working on is clean and dry. Hydraulics do not like water and dirt. Hydraulic pumps internally rely on a very tight fit for sealing the high pressures they generate. Dirt in the oil can destroy the tight fit and cause expensive repairs. And make sure that the system is not under pressure while working on it. Most systems have a relief valve for this purpose. This is especially important if the system has hydraulic accumulators because they can retain pressure long after the pump has been switched off.

We use the Kubota RTVs at work, they are almost bullet proof. They are in use 24/7 and lasted for years if maintained and not abused. The main breakdown points were the battery (but that was because of all the extra stuff that used power)and the radiator/fan (100f+ for weeks in summer).

We also replaced the wheel bolts with studs/lug nuts because those fine threaded wheel bolts are a pain to get aligned in the dark.

My father-in-law has a Kubota UTV. He has constant problems with the air filter getting clogged with grass and dirt. The filter placement makes it very hard to clean as well.

Maybe you should try a quad with all-season tracks before buying an UTV with wheels? Maybe you can rent one somewhere?

Looking at some video's the benefits of tracks (bigger ground clearance, large contact area so reduced ground pressure) are pretty substantial. There are some video's comparing the same quad with tires and tracks. And the tracks seem to deal a lot better with mud, snow, water and rocks.

Of course you know your terrain best, so maybe a UTV with a dedicated freight bed works better than a tracked quad. But from your posts I get the feeling that you basically cannot traverse the swamp with vehicles part of the year. A tracked vehicle might change that.