Load ranges for tires

I have a 97 Explorer, XLT, SOHC. I've decided to go with the Michelin LTX AT tires to replace my worn-out Firestones. The question is, will load range "C" or 6-ply tires degrade the ride quality compared to 4-ply tires? What are the added benefits, if any, going with "C" -- better puncture resistance and load carrying?

There's about $10 difference between the two.

Thanks in advance.