I use both the crankcase and starter housing Outerwear cover on my 5ive-T.
I can think of 3 factors to consider to determine if you need a cover or mesh mod; driving surface, rig characteristics, and environment.
Driving surface: Parking lot, groomed park, cemetery

, beach, you probably don't need either one. Unimproved field, construction site, you might want to use them.
Rig characteristics: I'm not sure what a Baja, 5ive-B, Dbxl or Mtxl does. My 5ive-T seems to pick up everything it runs over and throws it into the chassis tub.
Environment: Where I live there is a lot of Cottonwood trees. There are days during the summer where it looks like it is snowing, there is so much cotton in the air. The cotton doesn't seem to be an issue with automotive radiators but, on water cooled lawn equipment it clogs up the radiators screen and cause over heating. I'm worried cotton and weeds I drive through would clog a mesh mod so, I use the Outwears.
With the Outwear, clean up is a breeze. Just toss out big clumps of debris and a quick blast of air under the engine from the compressor and my rig is clean.