I finally felt the need to do some more GRBL testing.
TLDR - GRBL is more capable of data throughput for raster Laser image burning. It can handle approximately 4x as much speed/data as Marlin. For CNC use, I see absolutely no difference, so you can use either.
Why Not - Since day one of this CNC thing everyone has been telling me to use GRBL I did initially test it a long time back. At that time 3D printing was a major use case for the MPCNC so GRBL was a no go for that reason alone. Then with Bart Drings ZenXY / laser board I started to use it a lot just because of the board, real world use there was no difference between it and the ramps I had on there.
Another reason was no displays were available, you had to be tethered or use a Pi. Last I test V1Pi was not athing yet. That was a no go, I did not want a computer in the dirty CNC environment. Currently, it looks like a ESP8266 or better would be a good solution (good solution for Marlin as well).
So for the pretty basic raster tests I have been running with the Rambo Marlin could get to about 22mm/s before it would hiccup and leave artifacts in the image. Slightly faster with a 32 bit board at 28mm/s. GRBL on a Rambo let me do flawless raster at 81mm/s, but I went all the way up to 150mm/s and it would hiccup but NOT leave any artifacts in the image. Something about the way it handles speed, acceleration, and laser power is far superior to Marlin’s current system (9/10/22).
Again in terms of CNC cutting I do not see any differences. Cut and travel moves are far far less data than a Laser Raster burn that changes info every .19mm at high speeds. In CNC we move at slow speeds and change data in terms of many millimeters to meters. Plenty of time for processing and buffering.
I do not believe there to be any acceleration differences (other than laser/pwm) between the two anymore. GRBL used to be slightly better, I think they actually use the same equations for XYZ these days.
GRBL on a rambo is simple - John Boiles made a flawless dual endstop port of GRBL pre-configured for our Rambo’s, so flawless you can flash between GRBL and Marlin in a minute or two and not have to change a single wire.
Figure out a headless solution in addition to V1Pi, If you have a Pi do this for GRBL or Marlin. I would like to figure out a way to get the extremely inexpensive ESP8266 or ESP32 worked out to work with both Marlin and GRBL, on the Mini, Rambo, and SKR Pro.