I’ll start by saying that there is no such thing as a legitimate review of gutter protection done by climate. I’ve seen many review sites, the best known is Consumer Reports. Unfortunately in their assessment, they did not control for climate.
Here is Wisconsin the main thing that people overlook is quite possibly the most obvious one — that metal conducts cold. Since metal conducts cold it tends to freeze on contact in many, if not most, cases. If you live in a northern climate, regardless of how much of a nice guy your salesman is, do not purchase gutter protection with metal in it.
Rather than go through a litany of gutter protection types, my advice is simple — only purchase it if you believe it will work in your climate. There are instances where a product that works great in one area will be virtually useless in another.
Many of the sites that claim to be gutter protection review sites are just shills for the product that they want to steer you toward. They “test” under optimal circumstances in climates where water never freezes outside.
Some products will work great with normal leaves, while others are effective against pine needles. Understand this — there is no such thing as a gutter protection system that works in all climates against all trees.