I like gutter screens.
I think that they are the least expensive, most effective form of leaf protection. Not only that, but there very easy to install. Typically they come in 3 foot sections that you tuck under your starter course of shingles, then hook on the front lip of your gutter. A zip screw through the top edge of either end and your done.
Besides being inexpensive and effective, another one of the benefits that gutter screens have over other forms of leaf protection is that most styles are easily removable. This allows access to the inside of the gutter so you can re-seal any leaky end caps or miters and tighten or add fasteners as needed. Also, they leave the entire top of the gutter open to accept water. This is important for your gutter to do its job properly.
Some reasons not to use a gutter screen.
If you have pine needles or maples trees with “whilrybird” leaves, you might want to consider another option. Both have a tendency to stick straight up out of the screen. Some types of cottonwood can be a problem as well. Their leaves will eventually all dry up and blow away, or wash out through the gutter, but can be unsightly.
What type of screen is best?
You should always use a screen made from the same material as your gutters. Dissimilar metals will react to each other, causing a premature failure.
Always use the heaviest gauge screen you can find, especially if there will be snow and ice on top of it.
Some screens are made with a fine mesh on top. This may solve the pine needle and whirlybird issue, but they tend to freeze over rather easily and can be a problem in colder climates.
Plastic or vinyl screens are OK, but tend to fail in extreme temperature fluctuations, stain easily and don’t have the longevity of metal screens.