Hi Dars,
I have used both machines extensively with mouse embryonic stem cells. Both work great in terms of efficiency (>80% of green cells with the pmaxGFP reporter).
Neon is nice because you only buy one kit and you only change the electroporation settings between cell lines, whereas with Amaxa you need different kits for different cell lines. And it is much cheaper. If anything II found that viability is less good than with Amaxa (for mouse ES cells) but it not too bad. And I find that the R solution in the Neon kit goes bad after a couple of months but if your turnover is faster that should not be a problem.
For these reasons if I was to buy a machine I would pick the Neon system but you should definitely ask for a demo to test both machines on your cells before you make any decision.
Switching to these electroporators from lipofectamine was night and day for my genome editing.
Good luck with your experiments!
Elphege