There’s actually a few different ways you could connect to an E1/E2 via groov. Looks like @nickvnlr is talking about the new in 3.5 MMP support (vs. [Modbus Device](http://www.opto22.com/lp/modbus_support.aspx or a Data Store device connected via Node-RED, for example).
As far as going “direct” (Modbus is the most direct pre-3.5; MMP 3.5 or better) vs. other, that can same some $$ if you don’t need a controller in the mix, and remove layers, and be a bit zippier.
My “remove layers,” I mean you don’t have to worry about what happens when you lose comms between the controller and the I/O unit. Of course, you do have an auto-re-enable chart for all your controllers w/I/O units, yes?