I think Peter is narrower, as I could not fit in it when I visited the shop but could get into P2. But I was traveling and might have had feet swell in ways they wouldn't today so check with Vass to confirm.
Wearing my first Vass today, a budapest derby on the P2 last. It is the most comfortable last I've experienced out of the box and I've worn Carmina Simpson, Uetam, Rain, Detroit and Enzo Bonafe 946. Its possible I go the whole day with them, which would be a first for calf leather. The other shoe I worn an entire day out of the box is a Carmina on tarnsjo leather. Amazing quality. Love them. Can't wait for my soon to come F last shoe.
Trying to imagine the feet that could wear both Simpson and P2 .... Cant.