CNC hardware: Servo-Lite vs. Full-Servo with EMC

Hello Everyone,

I am planning to purchase a Shoptask that I intend to convert to a 4
axis servo based CNC machine. I am expecting to run EMC, but I
understand that it does not fully support lath functionality, in
which case, I would like (depending on the hardware trade off) to
have the option of being able to run other packages, so my preference
would be for a hardware solution that is not only compatible with EMC
but also with other packages. I would also like to incorporate
linear encoding with a feedback loop to compensate for backlash,
which EMC I understand supports.

I have read up on the subject and with respect to a full servo based
solution with EMC, there appears to be two approaches, one based on
the Servo-to-Go (STG) card and the other on a parallel port interface
solution from Pico Systems.

1- From a performance standpoint, what is the difference between the
STG solution and the parallel port based solution, and what feature
(s) does one offer that the other doesn't? Note that tachometer
feedback and variable motor speed capabilities are option I will be
envisioning as future upgrades.

2- Are any of these two solutions compatible with any of the other
software packages that normally use "stepper/servo-lite" based
controller hardware?

3- If for compatibility issues with stepper style interface programs,
I were to go with a servo-lite type motor setup, and if there is
linear encoding feedback into the EMC software, what is the tradeoff
in performance as compared to the full blown servo set up using
STG/Parallel solution with linear encoding feedback. It would seem
that if we have linear encoding feedback, both solutions (full-servo
vs servo-lite) should perform similarly and if so the servo-lite with
linear encoding feedback would be the preferred approach so as to
have backwards compatibility with other software packages.

Thanks for everybody's help and feedback.

Alan+