Don't even pay attention to ply rating. There is NO standard for "ply rating" and is subjective. One company's "3 ply" may be just as thick as another company's "6 ply".

I had BFGs on my Jeep and put 5 plugs in them in two years, four of the punctures I got right up around my farm property where the barn and house have been up since the 1940's and thru numerous roofings, additions on the barn, coop building, etc. over 70 years, there is just a mess of nails, screws, etc to pick up! Replaced them with Nitto Terra Grapps with a LESSER "Ply Rating" and I ain't had one penetrate the tread all the way yet. The FCIIs on my truck have seen the farm probably four times to every one time I take the Jeep up there and with the same "ply rating" as the BFGs I had on the Jeep, I never had to plug one of those either. Pulled a few out, but again, they never made it through all the way.

Now if you were to look at "Load Rating", that's a different story. There is a national standard for that...