Kubota w/loader front tire question

[strohman]

I have a 1975 Kubota L285 with the front loader. Its time to replace the front tires. It has 5.00 -15 4-ply 3 ribbed tires on it now. Lots of plugs in them-(the guy I bought it from did a lot of deer feed-lot planting). I found some American made Carlisle 4 ply and some China-made 6 ply. They`re the same price. I prefer the USA tires, but was wondering if the 6 ply would be better. Haven`t found a USA 6 ply tire yet. Which one would you buy?
Thanks.
strohman