Rubber is a bad idea for a bench you intend to solder on it, and it catches and holds pointy things badly.
I'm 100% with Mike, though not masonite specifically. Tempered Hardboard is what it's called generically. I picked some up for some partitioning to keep my ferret out of some off limits areas and it's great. **broken link removed** to what I think I may have used that I picked up an Home Depot.
It was extremely dark brown, and was almost as stiff as sheet metal, it was full hard all the way through and both sides were as smooth as glass. You can get cheaper stuff that's fuzzy on one side and only surface tempered on the other but the full tempered is incredible, I had some scrap leftover after I was done and tried to use it as a cabinet backing and it kept bending the finishing nails I was trying to use...
I picked up some cheaper stuff on accident for my bench (which still works fine) it's just not as bullet and scratch proof as the full hardened stuff. All that takes to clean it up is a couple swipes with a rag, nothing sticks to it, it's not really moisture friendly (especially the cheaper stuff) but that's generally not an issue.