Firmware

So I am working on a laser cutter and 3d printer with a toolchanger similar to the E3D design with kinmeatic bearings and a servo to lock in the heads. I was wondering which firmware I should use and have been looking at GRBL for the laser cutting but quite like the features in Marlin for 3D printing and so have come here for some advice as to which firmware I could use on my Arduino Mega 2560. Would it be possible to use more than one firmware? This is my first time using an Arduino even though I have a fair amount of experience with Raspberry Pi and using C/C++ so any help is greatly appreciated.
Thanks,
Max