The only problem I had with our slide was after several miles on a dirt, washboard road. One of the nuts that holds the slide to the extension ram came off and the slide wiggled out a bit. It was an easy repair and makes me wonder if the manufacturers have ever heard of Locktite! Anyway, I love the slide. You can get a shorter overall unit with the same living space as a larger one w/out a slide. Some things to consider with a slide: can you access your fridge, sink, bathroom, and cabinets with it in? This is nice while traveling so you can snack or pee w/out having to open it up in a parking lot. Does it have a backup system? I imagine they all do, but check. If you battery dies you don't want to be stuck with it out!
In theory, a trailer without a slide has one less thing to go wrong, but I think the benefits outweigh the drawbacks.