As Adrian says, the machine is important. Having said that, long experience tells me to look for the following:
Weight - believe me you will run close to and above the legal spec if you get a 2.8 ton van so go for the heaviest version available, 3.5 being the best. If you don't you will pay in tyre, suspension and brake wear, handling and legality.
FWD rather than RWD. I know this will get people going suggesting that Mercs & VW are the best (both being RWD) but FWD means easier loading of gear through rear doors (no kerb to assist unlike side door).
Length - modern terminology is L2H2 for the van you suggest. It is tight on space for a TM but going to L3H2 makes parking very difficult in such long wheel bases as the Peugeot/Citroen/Fiat and Renault Master.
Layout of van - sub-mount if you can - reel or no reel - shelving - position of fuel tank - heating and/or insulation
We have an Everest 650HP in a Renault Master L3H2. Machine is too heavy for a sub-mount tank so we have a 650L tank across the middle. The van is a pig to park and manoeuvre but anything shorter would compromise what we can get on and the way we work. Hope the photo displays!
Don't skimp on the set up as it will affect how you work for years to come.