I like wood benches - I just wish they'd last longer. I built some multi-level wood benches several years ago from pressure-treated ground contact lumber and dipped each cut end in copper naphthenate. The ends were an ugly blue-green where the wood wicked up the solution and the smell never completely went away - but those benches lasted long after I needed them. Never had a slug problem in that greenhouse, either.
The benches beside the new bench are almost 15 years old and no rot
so far. On the other hand, I built some cedar step benches, didn't seal
them and they are starting to rot. I hate it when that happens!