Excellent source of information is at this Lance specif forum
http://lanceowners.hoop.la/forums
On the Lance manufacturers website you can download brochures with camper specifications by model. It will show the weight, size fridge, sizes of the holding tanks, number of batteries that can be used (without modifying the camper).
Biggest differences will be in whether the camper has a dry bath or not. In general a dry bath makes for a much heavier camper. We use the campground showers or do a navy bath so the type of bath, wet or dry makes no difference in our enjoyment with our camper.
Two batteries make a lot of difference when boondocking. I added a second battery to our camper and we could go for 3-4 days without needing to charge them. I later added solar panels which charge the batteries in a few hours to 100%.
With the earlier campers some had a 4-season option that provided for storm windows and a tiny bit of extra insulation. The windows part is good at minimizing condensation inside the camper.
The campers with a basement will have a higher center of gravity and more steps getting up into the camper but also offer more storage space and different dinette configuration.
Having to install a new furnace or fridge can be very expensive so a good idea to verify that they work properly. Easiest to test the fridge by plugging the camper into 110v AC.
Look for any signs of water having gotten inside the camper. Often the caulking on the roof has not been properly maintained and water will find a way into the ceiling and walls.