We have a LWB hi top maxus (the beast) it swallows everything, we have 1000 ltr tank dual 2 man set up, working poles plus sl2 and gutter vac poles all high up in the roof, racking for all the rags, chems, gutter nozzles, etc...
And still enough room for a genny, gutter vac, pressure washer, wheelie bin, FSC, ramps, toolbox, electric reels x2 and most other bits and bobs.
This is used for large commercial work, heavy 2 man days, or gutter vac'ing and pressure washing days.
Our other vans are strictly window washing only and are smaller (but 2 man) carrying the minimum of poles, tanks,telescopic ladders and trad gear
A large van is great to have
Darran