If you live in a wooded area and a lot of leaves will be falling on your cover, you may want to go solid. Decomposing leaves on a mesh cover can create a tea bag effect into your water. If that's not an issue, a mesh cover is usually lighter and easier to handle.
Solid gives more wiggle room for having no algae growth while closed. At the cost of weight and needing a cover pump.
I have Merlin Smartmesh, have opened clear every year (mid-April) and close early November. I also have no winter leaves which remain on the cover. It is taught so even a gentle breeze clears it of leaves in my case.
Weight is the deciding factor for me as I often do it myself and don't need to hurt my back. To transport I use a hand truck. Since I open clear with mesh, solid is of no benefit there. In 24 hours my robot has any additional debris that got through the mesh out. But my debris is likely blown under the edges as it lifts in heavy wind.
I had to order a new safety cover this year and had this same question. My old cover was mesh. I was experiencing the tea leaf problem mentioned above which was partly a problem of an old "porous" cover and probably not installing the cover taught enough to keep leaves out of the water or lowering the water level during winter.
There are covers out there that claim 99% UV protection and are still lighter than solid covers and they have a better warranty than solid covers. I talked to several vendors while researching and they all said that if I currently have Mesh stick with Mesh. Once I heard that I decided to go with a 99% UV Block Mesh. Kinda made sense to me. I found no good reason to buy a heavier, more expensive cover, with a shorter warranty. I ordered the Mesh and plan to make pay more attention to either tighten the cover and lower the water level to keep water out of the water.