Here are my thoughts after using the bench for a few weeks.
The hubs protrude more than a steel vise screw head, but it's only a bit of a nuisance on the slider, I don't even notice it on the fixed vise.
The wood screws move 1/2" for each revolution. My Record vise, only 1/4". This is important because the wood screw doesn't have a quick release.
Strength is not an issue. If you have a properly built vise with a screw with the specs of the Big Wood Vise screw, you're not going to run into breakage problems unless you are intentionally trying the break the screw, even then it would not be easy. My vise chop is lined with leather, and with moderate pressure, nothing moves. I don't come close to tapping out the potential clamping pressure
The action is every bit as smooth as a steel screw, and there is no in-out slop in the threads. They are very precise.
IMO, it boils down to price. I spent the extra on wood, about $50 more per screw/nut vs. steel. I also like the looks of the wood vise screw. I'm pretty utilitarian when it comes to shop furniture, but a nice touch here and there makes the work environment more pleasant.