I have both the 50/1.2 GM and Q43 and love both of them. I have many other lenses in that range, but these days, the others seldom come out of the cabinet.
50GM
Incredibly sharp, even wide open. Very well corrected but yet nothing “clinical” about its rendering. It has really lovely bokeh that allows you to create moody, dreamy scenes when you want them. Its sharpness, colors and corrections make it a stellar landscape lens as well as its obvious use for portraits. It has respectable magnification at MFD. between it and the 135GM, I almost never use my nice macro lens any more. I find its weight perfect, but I don’t shoot with a 7c/R body to be able to comment on balance there. Easily my favorite lens.
Q3-43
Lens here is stellar as well but with its shorter focal length and tighter aperture, you mostly will have images with what I would characterize as “documentary style” or almost reportage. This is not a critique, but it is a difference. I am usually an overpacker, even for short trips, that involve photography. I have taken just the Q3-43 on several recent trips and got every shot I wanted, never missing the bag of gear I would have otherwise brought. That has been fun. Sure, in theory I could have just taken a camera and one lens and likely had a similar outcome, but there is something psychologically freeing about not having the option to pack another lens. With the new firmware, focusing is accurate and pretty snappy. AF is comparable to a7Riii. I added the Helium grip and found that very helpful for the ergonomics. I have a bit of a hand tremor but have yet to take a photo that is less than tack sharp, in spite of the camera “only” having lens stabilization.
The two options you mentioned have VERY different price points. You could basically buy another Sony body AND the 50GM for the price of the Q3-43. Or, you could buy the GM and take a spectacular trip…or buy three Sony GMs.
Even if you are willing to drop $7k, you should still carefully weigh the best use of that kind of cash for your needs and interests.
Jim