PlUS - keeps leafs etc off the top of the slide, directs water during heavy rain storms away for the gaskets on the top of the slides. Will keep the hot sun off the slide roof and help - somewhat keeping the RV cooler.
NEG - flexible surface should be cleaned to keep dirt and mold off them, I find dirt, dust, pollen does collect on the slide roof when open - so unless you want to bring that into the camper you need a long handled mop to clean off the roof of the slide or you will what has collected under the awning inside. Slide topper material hat will deteriorate over time and need to be replaced.
It's a personal and financial decision every owner must make, mine came on my Bighorn so my decision was made for me. I would probably get them again, but maybe not white.