Master Technician Kristen and Bandit the Shop Cat explain different dryer vent covers.
Dryers live or die on airflow; vent covers are often a sticking point. Meant to keep pests out of the dryer venting, vent covers can be blocked open by lint or trap lint so that it blocks airflow and becomes a fire hazard.
From our decades of experience, we feel that the best vent covers for dryers that vent on a wall are the "Dryer Wall Vent" and "The Defender" from In-O-Vate (Inovate.com). Made of high-quality powder-coated steel, they are designed to last decades. (For roof vents, we recommend the DryerJack by In-O-Vate. Not shown in the video.)
The plastic louvered vent cover is a distant second best after the In-O-Vate products. The performance is acceptable, but the plastic disintegrates after a few years.
The aluminum vent cover is a poor design but is cheap and widely used.
A grid over the dryer vent will trap lint and is against the building code because it is a fire hazard.
(We recommend In-O-Vate products but do not get any remuneration for doing so.)