Welcome bud!
I know a few lads here have imported their vans and hopefully they can give you specific advice on that. I personally preferred to buy locally, less hassle and since I spend most of my trips within the island it made more sense to have a right hand drive van.
As per reliability, I would say that they're are all pretty much on par, it's just a matter of the maintenance that they have received. So look for an obsessive owner and a good service history more than a specific brand.
It's great that you have a particular layout in mind, to me that's one of the most important things to consider and it's 100% personal preference. That also might make you fall in one specific brand or the other..
Both Fiat/Peugeot chasis/engine are well known true and tested can't really go wrong with either, but do let us know what year range are you looking for and we might be able to tell you if there's any specific know issues with that specific model.
Happy shopping!!
Rami