In terms of achievements, obviously Djokovic is better. But, Del Potro is younger.
Both have 1 slam, beating the GOAT in the process. Both is fairly consistent (well, not recently. But, overall they are).
H2H Djokovic leads 3-0. But their last meeting was before Del Potro won his slam. I think Del Potro is better now.
What I want to know, who do you guys think between these two, that has the better game? Which one is more talented? Which one will ultimately have the better future?
Well, the answer for the last question will be speculation, of course. So speculate away!!
Big difference is that the argie defeated a healthy Federer
Apart from that, Djokovic is a better and more complete player