Think I was talking to the same owner yesterday about this same boat. Since I can't get get into Canada to look at any of these boats, I haven' made an offer on them.
From what I can determine, it looks like the 310's aft cabin is very small and extends aft under the cockpit area. As the owner told me his 16 yo granddaughter stayed there, but it was tight for her. From some pictures I have seen, it looks very tight and most use the space as storage. The 300 doesn't have the space, so I believe the dinette is a bit longer.
This also was one of the first that I have seen with a diesel engine. Some things that makes me wonder, I was told that the boat had a 32 US gallon holding tank, 200 US gallons of fuel, but only 26 gallons of fresh water. I was told that they drink water from the lake after running it through filters, and that the tank was aft near the steering gear.
I though the price was a bit high, but considering it came with a dinghy w/motor, complete canvas, and had a Yanmar diesel makes me think it was priced reasonably. If I could get into Canada I would try to buy the boat. I think it would be a great Loop boat.