IM is a great game. I don't think you can go wrong with either version. Personally, I think I'd prefer the Vault if only for the fact that everything is all newer inside as far as the electronics go.
I'm hoping to pick a minty one up either in Allentown or at Pintastic this year. GL in your search too OP.
Edit:I knew someone else asked the same question. Here's the link for you OP.
https://pinside.com/pinball/forum/topic/help-me-choose-imve-or-original