The R800 is a current model and is A4. It uses the original Ultrachrome HiGloss inkset.
The R1900 is an A3+ model, with updated inkset and LUT and other advantages. It uses the new Ultrachrome HiGloss 2 inkset.
The R2880 is an A3+ model using the Ultrachrome K3 with Vivid Magenta inkset.
Pro 3880 is the newly updated 17" (A2+ basically) model using the Ultrachrome K3 with Vivid Magenta inkset.
Of those, only the 3880 has networking built in. The others have no option for networking from Epson, although you can share them via a computer and some (but not most) printer networking hubs (because most don't support bi-directional communication, so they may print, but you won't get ink levels etc).