Both replace the tub with an alloy body, but they are built for different work.
The T Series is one chassis-mounted service body: 2.5mm aluminium in black powder coat, two large side-opening doors, underbody storage boxes, mudguards, and front and top Unistrut rails. It suits trade work where the load is tools and stock.
The H Series is a tray with a matched canopy on it. The tray runs a 4.0mm deck floor with a built-in 40L stainless water tank, a trundle drawer, side boxes, mudguards and a headboard - no drop sides. The canopy has a roof platform, spare wheel mount, jerry can holder, rear ladder, four-point locking and jack-off capability, so it comes off the tray when you need a flat deck. It suits touring and anyone switching between gear and loads.