I have a lot of respect for poly. Its very tough. I told on here before about having to rehab a rental unit that belonged to my Dad 2 years ago. The hoarder that was living in it totally wrecked the place. The kitchen cabinets that my folks had put plain old minwax poly on sometime in the late 80's were caked with grease and grime from some 19 or so years of never getting cleaned (previous tenants before hoarder were decent). I took the doors off and cleaned them with a really strong ammonia and water solution and the grime just oozed. But to my amazement, the finish underneath was still stuck on and looked pretty good, just a little dull. Being an overachiever, (ha!) I scuffed them with 120 grit sandpaper and went back with a couple of fresh coats and they looked brand new. That is the great thing about it, if you want to freshen it up you can just clean/degrease, scuff, and give it a fresh coat or two.
IF the bench is going to be inside a shop, I would not go with the outdoor version. I was gonna do that on my cabinets because I was looking for the toughest thing going and found online that the outdoor finishes are softer/more flexible to help stand up to UV and the elements....they are designed for expansion and contraction. The indoor stuff is harder and more abrasion resistant which might be a little better on a worktable.
