Tsunade takes this.
1) Hidan isn't smart enough to know the affects of Tsunade's jutsu so even if he gets her blood, he'll stab through a vital organ and try to kill her that way and shit won't work, cutting off her head would be the only real way, and if he did that he's pretty much loose himself as he wouldn't be able to re-atach his body, thus eventually he'll die it'll be a stalemate in that situation, although if you want technicalities, Hidan will still be alive. so he'll win but only in that scinerio.
Now both are equally as fast if we want to follow data book rulings so it's completely possible for him to cut her, and for her to obliterate him in a single shot. Now what people don't understand about Hidan's ritual is that, he needs the blood then he needs to make the ritual circle, which will take some time, time that no idiot would give to him, knowing of his abilities.
Why does Tsunade know of Hidan's abilities and he doesn't know about hers? Info from previous battles have been relayed to her. The thread was vauge so I assumed we're going by if we manga and anime docterine to help us decide this.
Now Tsunade has more then enough power to pop Hidan's top off, but Hidan's jutsu isn't instant so getting blood from her is the first part, setting up the circle is the second part. Flaws like that can be exploited. Also those defending Tsunade forget the Medical Creed, that of saying Medics are defensive fighters, they are the last to be killed in a battle. Tsunade is naturally defensive because of these creeds she, herself created and that gives her an ability of advantage. Yest both are the same relative speed but you'll have speed playing with a skill set of offense with no formal emphasis on a perticular style of fighting (Hidan) and swings and fights more or less recklacelly. You'll have that against a speed with a skill set behind it designed or defensive movements, evasion, and avoiding getting injured, as that is the style of fighting Tsunade specializes in. So the feat of getting blood from her is much more difficult then it seems. Don't talk about what happened in part one when she was inactive as a shinobi for 20 some odd years and had a fear of blood.
I'm almost certian if Sakura can take a blade through the torso (or stomach or wherever she was hit with Sasori's sword) I'm sure Tsunade's resilliance is enough to sustain if she's stabbed through the heart or internal organs with Hidan's blade if she has the regenerative technique active.
Also her body points confusion technique, that she used, if that makes contact with Hidan at any point in time, he's screwed royally unless he can discern which functions have been confused quickly.
Overall we have Tsunade besting Hidan in a close range fight because of her body points jutsu, her superior taijutsu capabilities, her strength, and her ability to avoid being hit, as is the method of the medical shinobi. Hidan will have a more difficult time dealing with just getting her blood, setting up for the ritual is another thing. However Hidan has no real defense against her power which is enough to render him incapable of fighting.