I have flow the 310 (P,Q,R) models and have only flown 1 turbo model once. Most of the R models are either 285 or 300 horse. The P-Q are 265 I think. I would get an R model if it were going to be flown for 135 cargo/charter. The Turbo yielded small benefits bellow 9,000 feet. If you plan on crossing mountains or long haul type flying (more then 500 miles) then a turbo may provide some benefits. In the charter/cargo field were you cycle starts and stops frequently the turbo will be a hindrance were maintenance is concerned.
As mentioned a know Ice 310 would be a necessity were you live. Actual "known Ice" would require a heated windshield and most do not have that. Either a whiskey window or a hot plate. Try to find one with inboard boots as well.
Single engine performance is not that bad in the colder months if you are modestly loaded. It handles ice fairly well. The prop heat pads are the key, clean props can pull a dirty plane.
Any 300 and 400 series Cessna have the gas heaters up front and can be a source of maintenance. They should be treated like a turbo charger, cooled down etc. If they get overheated in flight, you cannot reset the breaker until you land, as it is in the nose gear well. So that can lead to some cold flights.
The R models seemed to burn 18GPH or 36 total. With 160 gallon tanks, this would give you about 4 hours flight time with a modest reserve. Cruise in the R models at 8K feet usually yielded 170 knots.
All in all it flies and handles well. The 310 is more squirrelly then the 400 series and requires you to fly it almost all the time if there is no autopilot. It would not be my first choice for a passenger aircraft.
Mark