Hi Susan, I've been watching this thread and Bedlam, Jefe and others have given you some great advice. We switched from a 19' TT to a TC a couple of years ago and did a lot of research which turned out well. We also wanted to do winter camping, as we have a project ongoing to ski 100 ski resorts in North America.
> We want to buy used and we want to do some winter camping so we'll need an all season or four season package.
Used is a great idea. We saved about 10K off the new price buying a 1-year old rig in perfect condition.
We have an Arctic Fox which has good insulation for winter use. Most of the TC's with heated basements will do. Some brands that are good for this purpose would be Northern Lite, Bigfoot, Arctic Fox, Lance, Adventurer, Eagle Cap, Host, and Northstar.
> There are so many brands! Is there a brand that is more well-made than another?
The fiberglass shell brands Northern Lite and Bigfoot are probably more durable overall (and expensive) due to the fact that they are built like boats, but you are splitting hairs here. They all need to be maintained and like all RV's they are all built as cheaply as possible to produce profit.
However, it sounds like you need a slide-out due to the fact that you are downsizing, so you will have to go with one of the others. Note that all slide-outs are not created equally. For example, the floor space (width when slide-out is out) and dinette size are larger on an Arctic Fox 990 than in the 811 by a few valuable inches for some reason. Take a measuring tape when you look.
> We don't want a monstrosity since we don't want any issues with drag on some of the dirt roads we may encounter. But we do want a slide out.
If by "drag" you mean "height, width, and weight", these requirements are really in conflict. TC's with decent-sized slides are heavy and large. Trees are the biggest problem because the TC's are so high. Maintained dirt roads in forested areas are fine. Unmaintained in the desert can also be fine, but the amount of unsprung weight on the rear axle makes the going slow. Any type of bouncing or back-and-forth swaying gets things moving a lot and it's not that fun even though it is possible.
You should also consider tank sizes since it sounds like you will be dry camping with no hook ups. When we were looking we zeroed in on the Lance 992 and Arctic Fox 990 after going back and forth between the two at an RV show. The Arctic Fox was cheaper used, so that's what we ended up with. Others of note included the Lance 950S, Adventurer 910FBS, Host Cascade, and Eagle Cap 995.