The way I see it, Movie 7 Goku and by virtue Android Arc Goku really aren't that far off from Future 17 in the first place. Especially considering that in movie's 7 case Goku here may be just as strong or stronger than SSJ Vegeta whom I have no problem putting decently close to Future 17.
No. 13 was treating his fight with Goku as a joke.
#13: "What's the matter Son Goku? I'm just barely getting warmed up!"
And its clear he has Goku on the defensive during the whole fight. To me, if that doesn't say 13 has a small power advantage then at best, he and Future 17 probably rival one another and at the very least, No. 13 has techniques on his side.
Not to mention (though I'm unsure how well it would play a part here) has the Supercomputer pumping in data for him.
I give it to No. 13 in the end.