definitely Boxing. Wrestling is great in close range and it's good to be able to grapple/stay balanced on your feet and not be able to be taken down.
Being able to read punches, distance, and footwork will put you levels beyond the general public.
The ground is the LAST place you want to go though.
BJJ is useful of course however, it has been mystified to DEATH by mma, not everything you see on the ground is damn BJJ, it's mostly wrestling. The high level grapplers in MMA use WRESTLING. It's actually funny when they commentate and mention how good a guy's grappling is and credit it to BJJ...and then you find out the guy was an all american NCAA wrestler. Or how (insert fighter name) is a brown belt in bjj...and then they just casually mention that they come from a wrestling family and have been wrestling since like 7 or some shyt lol.
High level wrestlers can pretty much neutralize and out grapple most bjj black belts using their wrestling alone.
They give out these bjj belts like candy, and all american pedigree level wrestlers are not doing much to attain them. It's crazy how people are still stuck in the 2000's with the BJJ > mentality, that has already been exposed...but the UFC (because of Gracie legacy) and the countless BJJ schools across North America will continue to perpetuate it, it's a huge industry now.