Just came across this on random thread searching...
As a big Wonder Woman fan (but also familiar enough with Thor to have an educated opinion), it is simple: If it is a case of simple strength (say, they decide to arm wrestle over who picks up the bar-tab), then Thor will win (though it will take him a bit longer than he - or his fanbois - might imagine to do so). No question about that.
HOWEVER...
If we are talking about an overall fight - as some of the threads above seem to have drifted to at some points - then that becomes a *very* interesting proposition, and one I find much more well-matched than many of the other mega-slams, as both characters have themes of great physical power and the use of powerful mystic weapons. Thor edges Diana out in terms of raw strength and the ability to utilize powerful aggression in all-out attacks; he also can at various times channel divine power via Mjolner, and even greater strength via the use of his belt. Diana, on the other hand, is much faster than Thor (not merely in terms of movement, but reflexes as well), and has superior combat *finesse* and tactical skill, as opposed to Thor's (albeit very effective) more blunt attacks; also, her divine weapons (Hestia's Lasso forged from the very bosom of Gaia/Creation, and her vambraces, which are the current embodiment of the Aegis) are one of the few things in "modern" comic mythology that can stand against something as mighty as Thor's hammer.
Assuming Thor's belt is mitigated by Diana possessing the Gauntlets of Atlas (which are still around, and magnified Diana's strength to levels far beyond Superman's and Doomsday's, as drawn/written by John Byrne, and others)...
And assuming Diana's greatly superior speed/reflexes are mitigated by Thor pushing himself to the limit and/or using his divine power to compensate for that difference...
And assuming each has a *legitimate* reason to battle the other (genuine misunderstanding; fate-of-the-world-at-stake; b*tch/A$$h*le called my momma a ****, et al)...
Then we have a very, VERY good fight on our hands, one of the most well-matched (in terms of conceptualization of character) out of the majority of mega-slams, and one that could well-end in a stalemate, or both of them killing each other. (I'd say, in a 10 spread, that 5 out of ten they each KO the other after a drawn out fight; 2/2 split each kills the other; and a 1 in 10 that they each deliver fatal wounds to the other, resulting in both dying.) Only with the significant influence of outside forces/circumstances would one clearly defeat the other.
And for those who *TRULY* know both characters, y'all know that THAT is the real down-low about how things stand... take it or leave it... 🙂