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If its a good deal I wouldn't be afraid of the liquid cooled sled. Mine is liquid cooled. With a studded track and scratchers I kick up enough ice to both cool my sled and lubricate my hyfax. I've never overheated mine and I do some long runs pulling a sleigh, often on bare ice at the start and end of the season. Just get a pair of scratchers and stud the track. A studded track makes a huge difference in added traction as well. If you're worried about slush, a snowmobile is your best option.
I was from central Iowa and now moved to the Iowa line up in the NW corner. This past winter was the only one in the past 5 winters where the snow was too deep to get a ATV on the ice. And this winter the deep snow only affected the last 4-6 weeks of the season. I could still walk on the snow covered lakes, on bigger busier lakes somebody always drives a vehicle on and creates a packed path, so your atv or walking is still good. You will get much more use from an ATV than a snowmobile, in my opinion in Iowa.
An ATV may be usable year round for some people, but if the sole use is for ice fishing (assumed from OP) it can't do as much as a snowmobile. As a toy to use all year, a quad has a longer season but a snowmobile is a better machine with more capability for ice fishing. A quad is a good jack of all trades but a snowmobile is better at doing snowmobile things on snow, ice and slush
Disagree somewhat, this season we developed so much snow and slush that sleds were useless pulling anything out. Only vehicles that had any luck were ATVs/UTVs with tracks. Sounds like OP won't be running into anything like we had in Northern WI, so to put it in his perspective, he's probably better off with a sled.