It's obvious that she loves Goku more, but they always argue in the GT series; but with Mr. Satan she always talk normally, also about her problems.

I think Goku, and not because in Dragon Ball Gt they have traveled together, but because Goku is like a child

Pan has a better grandfather relationship with Goku because she has a lot more adventures with Goku than Hercule plus Goku taught Pan a whole bunch of moves and besides if it were up to Hercule we'd all either be enslaved or dead by pretty much every huge villain. (even Pilaf)

She trusts Goku a lot more so I think Goku.