If full timing, I would want these things:
1- 2 separate baths, or at least a half bath. My wife is a mess in the bathroom. We have separate bathrooms at home and it works very well for us :). Our camper has the bath and a half which is nice because I can do my business in the rear half bath.
2- Make sure your tanks are large enough that you don't need to worry about finding a hookup or cleanout. Our blacks @ 40 gallon each lasted us a full 2 weeks (80 gal total between the 2). Our grey is 40 I think? It lasts us 4 normal showers (ie: water running not turning it off) and some dishes before it's full. I would had preferred a 60-80 gallon but we only have a 36' camper. 100+ fresh water is ideal so you aren't freaking out if you can't find water. Most triple axle trailer double the capacity of all those tanks.
3- Kitchen or open floor plan kitchen is a must for full time I think. We have a peninsula style kitchen. It's functional and fine for our weekend style camping, but I could not live with that full time.
4- Figure out the length you will need. Shorter is better for campsites. Longer is better for full time. Our garage is 11' and my Ultra fits fine. I hold it far enough back that the antenna has to come off the rear pack or it will rub on the 3 season doors. That allows plenty of room for walking in front of the bike and getting to the half bath.
5- Check the stove. Some campers (like ours) has no counter space on either side of the stove. That is OK for our type of camping since most of the cooking is done outside and it was a compromise to keep the length short as possible with a full garage. However, for full time, that would drive me nuts.
6- Option it up. Make sure you have 3 AC units. If you travel somewhere warm, you will have enough cooling. If one goes down, you still have 2. Adding a 3rd to ours was only about $800 from the factory. Also make sure you have slide toppers. Full timing you will stay at CGs longer and all sorts of stuff will fall on your slide. The toppers will keep the slides clean of debris. Get the 3 season door so your deck is usable as a deck.
7- Forget the "residential fridge". I know they are likely better quality than an RV fridge, but I like having the propane option when traveling vs running the generator to keep it going. We have a 12 CF fridge and I think the largest on the market is 18CF which is pretty dang big.
8- Make sure you get a generator. Nothing worse than having no power at the campground and it allows our more places to camp (ie boondocking)
As far as brands go, we settled on a Grand Design. We are happy with it. The specs were better than other models we looked at. Better tires (G rated vs F rated), upgraded suspension with wet bolts, higher CCC, more cabinets, ducted heat/ac (no floor vents), more ambient lighting (under counter, above cabinet, etc).