After several thousand miles you can adapt to many things.
I will second what Beth said about slides in cold weather. I experienced that in my very first rig. My last rig didn't have heated tanks. When I knew I had to drive through really cold temperatures I would use pink stuff in the tanks until I made it home and could winterize or made it south and didn't have to worry. I never sat in one place long enough in cold temperature to have to deal with frozen closures.
Depending upon how you want to use your rig and who may be traveling with you, slides or no slides have everything to do with floor plans and space. Depending upon the size of your Class C remember that slides add extra weight and may leave you less carrying capacity. And as mentioned, check how useable space is with the slide/s closed.
Think about both inside and outside storage and the dimensions of the doors and what may or may not fit in places, and how you will be able to distribute weight so that heavy things aren't all on one side or over one wheel. Lots depends upon what is important that you want to carry with you.
Measure things that are important ( or even your comfortable camp chair
) and carry those measurements with you along with a measuring tape as you look at rigs.
My last rig stayed warm or cool quite nicely but I usually felt a little like I was in a cave because of the windows and the views. There are no answers that are perfect, only answers that fit you..... And most of us will admit to trade offs that we allowed ourselves to accept because some things were more important to us than others.