I've read only one or two Phantom comics, but I did watch the Defenders of the Earth cartoon as a kid. If Phantom has the power of ten tigers (whatever that works out at) then I figure he could physically take the Shadow, but I'm not sure if that's part of the comics continiuity. In comics he has guns. So if he's just a regular guy with guns, he's pretty even with the Shadow physically, but the Shadow's got that invisibility/mind mojo working for him as well as the guns. This being the case, I think the Shadow would take the win.