The mesh/breathable bumpers are generally considered safer than the thick padded rectangular ones since there's still some airflow, and they do help with the feet-getting-stuck problem. That said, some paeds still advise removing bumpers altogether once baby starts pulling up, so it's worth keeping that in mind as he grows. My girl was the same at that age, very wriggly, and the mesh type worked well for us as a middle ground between safety and keeping limbs inside the cot.