Black will show the most imperfections.
Acid dipping will take off everything, including parts of the car where rustproofing is hard to get at (sills, rocker panel, frame rails etc..) and previous filler if present.
Plastic, walnut shells, or other soft medium is a better alternative IMO since the operator can control where the paint is stripped. Leaving any previous filler saves time from having to reshape also.
Starting from clean metal is time consuming and costly. It really depends on how much you want to spend and what condition your existing shell is in.