While Hamlet of old labored with the question, "To be, or not to be," many RVers have their own soliloquy, "Slideout topper, or no slideout topper?" Ah, that's the question, we'll help you with the answer.
First, what is a slideout topper? Imagine an RV awning that extends itself, not over your "patio area" but over the top of your RV slideout. Most are constructed of heavy gauge vinyl, but unlike standard RV awnings, these automatically deploy and retract as you deploy or roll in your slideout.
What's the purpose of a slideout topper? Basically the topper is an added layer of protection over your slideout room. For a certainty, your slideout should be engineered and manufactured to take care of itself, that is, keeping the rain out. But the topper can give a bit of help. Camp in an area where there are trees? The topper keeps leaves or tree needles, and tree sap, from getting onto the slideout roof. Without a topper, when you reel in your slideout room without cleaning debris off, you run a good chance of pulling some of that debris right into your rig.
Perhaps you don't spend much time camping out in the great forests. A slideout topper will keep your slideout a bit cooler in the hot sun, as it provides shade over the often-not-well-insulated slideout roof.
With all this "good" stuff that comes from a slide topper, why would you not want one? A couple of things come into play. First, if your RV didn't come to you with a slide topper, you'll find out in a hurry that they aren't inexpensive. Even a small slideout, say one that's less than eight feet wide, can run you close to $400 plus installation. Have several slideouts, multiply the expense.
Others have found that slideouts can produce a lot of noise on a windy day. If you have trouble enough sleeping on a windy night, a flapping slideout can really add to your misery.
If you decide to add slide toppers to your present rig, a common comment from those who have them is this: Make sure they're wide enough. That translates to a bit wider than the slideout itself, NOT only as wide as the slideout. This will help ensure that the purpose of the topper really works out for you.