I have a Gamma 4000 and it's fine for a 1st stringer. I got mine for $500, about $150 cheaper than a Progression ST
The glide bar clamps are OK...it's just older technology but still solid. The Neos still uses that design. As far as diamond dusting, I can't comment on that, but I've had no slippage using the clamps without having to super-tighten the settings. I am satisfied with it as a personal stringer. It's worth about $500 and it's probably the best value in a floor standing machine with a manual crank. You will need a tension checker though.
I don't think I would go back to a tabletop after having a floor stander. I really like it. A Gamme 5003 is just too much money for me to justify.