Hi brittf,
I am not familiar with either controller, I use an ESS but have had occasion to read the manuals for both.
I was very impressed with the PoKeys offering because it offers MODBUS type functionality, that is to say it
can communicate certainly 16 bit and probably 32 bit numbers over its Ethernet connection in addition to
all the physical pins.
I am a recent convert to M4 so please understand that my opinions/assertions are subject to revision by others
with greater experience than I.
Historically SmoothStepper and PMDX were invented/developed at a time when all users were PP. As a consequence
their pinouts and so on reflected what their customers already had ie PP cables/BOBs etc. They retain that character
today. The ESS has 26 pin headers which with a ribbon to db25 cable is identical to a PP.
PoKeys has a slightly different origin as an I/O interface. The I/O is communicated to the host PC over TCP/IP. Additionally
analogue data once converted to digital can be communicated. The 57CNCdb25 is a conveniently connectorised version
of their 57E. Both can be used for M4 but the 57CNC is the more amenable to use because of its connections and pinouts.
All three devices (ESS, PMDX-411 and 57CNCdb25) are really good value for money with the flexibility of the Pokeys
offering making it very attractive.
Note also that Cslabs, Hicon, Gallil and Kflop also make controllers with many nice features but in most cases much more
expensive than those above.
All in all Mach4 users have a stable of good suppliers to chose from and any devices from any of them will work. If there is
a specific feature you require then go for it.
Craig