My dad is looking to get the roof on his house replaced in the near future, and we already know that the decking has to be replaced.  One of the contractors is recomending that wafer board be used in place of plywood.  After some research, I'm still a bit worried about the longevity and durability of wafer board as compared to plywood.

If any of you have experience with these materials, I would really appreicate your advice on this.

ViseGrip

Spend a little more and use plywood. If that USB gets wet, it'll start coming apart. My dad was a builder and he hated that stuff, he always used plywood.

Both plywood and OSB will swell/come apart when wet, but they have to have long term moisture  exposure to do so.  Modern plywood doesn't lay as flat as OSB and isn't as easy to install.  YMMV.

Quoted: Spend a little more and use plywood. If that USB gets wet, it'll start coming apart. My dad was a builder and he hated that stuff, he always used plywood.

It's OSB, as in Oriented-Strand Board. Like all building materials, there's good stuff and bad stuff. OSB that is designed for the application will last as long or longer than plywood. The resin that bonds OSB and plywood together is pretty much the same.

I just used wafer OSB that was approverd for roofing and 24" centers  seems to be fine- be sure to use the metal spacer clips on the seams.  I personally would prefer plywood,b ut at the time it was like another half as much.