The Ram ProMaster/Fiat Ducato is a lighter duty fwd van. SRW usually translates to less weight carrying abilities. In this case you might gain a bit of interior space without the RWD drivetrain taking up space.
Comparing the Winnebago Trend (ProMaster SRW), Fuse (Transit DRW) and View (Sprinter DRW) you can see the capacity difference:
Trend: 9,350 GVWR and 11,500 GCWR
Fuse: 10,350 GVWR and 13,500 GCWR
View: 11,030 GVWR and 15,250 GCWR