Whichever you pick, the inversion step is where most of the quality is won or lost, not the hardware.
Capture flat. If it's a camera, shoot raw and don't touch the in-camera profile. Set your white balance off the clear film base between frames (the orange mask), not off the image. Then invert in something that actually models the mask rather than just flipping a curve. If you invert in Lightroom with an upside-down tone curve you will fight colour casts in the shadows forever, and every frame will need its own fix.
One practical note for 6x7 on a flatbed: get the negatives flat. Curled 120 is the single biggest cause of soft flatbed scans, people blame the scanner when it's the film sitting half a millimetre off the focal plane. Anti-newton glass or a decent holder with adjustable height fixes most of it.
darktable has a negative module that handles this properly and it costs nothing. A flatbed with good software and a careful inversion will beat a camera rig with a sloppy one every single time. imo that matters more than flatbed vs camera.