Talzin being at "the heart of her power" (whatever the hell this means in practice) doesn't really make up for all the other negative circumstances she was coping with during the Sidious fight, whereas Sidious was at worst fresh and at best benefiting from any ambient Dark Side energy. So her feat against Sidious is likely to be at least slightly applicable here.
I doubt she lasts longer than a few seconds up close. Force seems fairly equivalent; I would envision Krayt putting up a great effort against Sidious but being on the clear back-end before long, just like Talzin.
If anything, I'll side with Krayt for his greater fighting skill and Dark Transfer.