>>4161515Trick question, mein neger.
If the APS-C is a Canon (1.6x crop factor) or Sigma (1.7x crop factor) then FF.
If the FF is a 5D3 or older Canon and the APS-C is a same-era Nikon, then APS-C. Outside of those fringe cases, FF all the way. Less taxing on the optics and usually better dynamic range, as long as the sensor tech isn't behind like Canon's was up to the 5D4. Some newer Canons suck too, like the RP. Beware of those and you'll be fine with any FF you pick.