For many years I had the version that was a strip of aluminum with a rolled front edge. There were little clips that held it in place with about a 1/8" gap under it. Water rolled down and curled around and into the gutter. the trash fell off the edge. Worked perfectly well for more than thirty years. Over the years it something of a beating and some of the clips got lost and a piece or two disappeared in the wind.
I replaced it with the type that has a fine screen on top. (They put the hard sell on it on TV.) I got mine for next to nothing at a freight auction. It's OK, but crap accumulates on it and turns into potting soil. I have to clean it off occasionally. Need to now and even though it's only about a year old it's obvious it's going to require a lot more attention that the solid stuff.
I seriously doubt the brush stuff won't turn into a giant strip of potting soil and you will have trees growing in your gutter in a year or two.
Gutter guards, HA! This house came with them. We had not heard of them previously. The other half was so excited that he would not need to buy a new ladder in order to climb the two story roof. We figured out the gutter guard racket the first fall here. They are since long gone and we are the proud owners of a 24 foot ladder.