Vaseline is just a brand name for White soft paraffin. 500g tub of WSP is cheaper then 100g Vaseline
I've always put vaseline around the tops of my hosta pots and so far never had a problem with slugs, the only problem i have is, i forget the vaseline is there and go to move the pots around and end up with greasy fingers! YUK!
We've been hatting about this on another thread recently - it seems to work for some people, but not here - tried just about everything to protect my hosta pots, all 65+ of them, found that really only copper rings work.