Great thread. I believe Gallo is better by a wide margin. Gallo can shoot, handle the ball, pass, drive to the basket, and is a decent defender. Chandler is a poor passer and ball handler, poor shooter. He can drive to the basket, but he gets to the hoop far less often than he should.
IMO, assuming no major injuries to either of them, Gallo will also have the better career. Chandler's game relies almost entirely on his athleticism. Once that goes, he'll really have nothing. Obviously a lot of things can change during the span of their careers. Maybe Chandler improves, but as of now, that's how I see it.
Once again, the mental edge has to go to Gallo. He has shown signs of being a leader and a playmaker. Chandler has always had questionable heart and seems to slack off a lot.
The better athlete is probably Chandler. I wouldn't say Gallo is nonathletic, but that's really Chandler main skill.
I would definitely trade Chandler if the right package came along. I wouldn't give him away for nothing, but I wouldn't mind parting with him if it meant we would get some nice pieces in return.