For many years, the Peugeot Boxer, Citroen Relay and Fiat Ducato have been the same vehicle. It's a Fiat-designed product, badged as Peugeot or Citroen as appropriate. Depending on what age of vehicle you buy, they're all likely to have been built in a jointly owned factory in Northern France, or (since about 2006), at a jointly owned plant in Italy. I wouldn't say there was anything to choose between them in terms of quality, durability or reliability. Same engines, gearboxes, vehicle structure, etc. We've sold a fair few Converted Peugeot Boxers over the years and I'd say they were pretty good, but no better than the Fiat or Citroen. If you plan on using a dealer for work, just pick whichever one has the best dealer in your area.