To begin with, the Epson EcoTank ET-1810 is only a printer in which no copy or scan functions are present.
The other three models are virtually identical, but the EcoTank ET-2820 series has a 3.7 cm colour LCD screen on the front, which the 2810 series does not.
As for the 2814 and 2810 models, they are basically the same in terms of specifications.
The only difference might be in the region in which they are sold.