I've owed both.
If given a choice between slide and without a slide, I'd go "without" a slide. That is correct. Without.
Slides have flat roofs and over time, they leak. Slide have rubbers around their edges and over time, they leak. They also let critters into the main chassis box as well. Slides also have moving parts. Moving parts that break and bind. And many slides stop the ability to pull over, use the washroom or have a quick rest in bed on kitchen table, then continue to drive. To use the insides, the slide must be motored out. Slide trailers take more energy to heat and cool as well.
I've own both and knowing what I know today, NO slide trailer is best for me. My next trailer will be without a slide.