I totally agree with this. A good co-founder is way more important than a few more equity points because it was your idea. It might be different if you've spent 6 months on your own building it, though.
I disagree about the dedication--I wouldn't even bother working with a cofounder who wasn't as dedicated.
It would annoy me if the co-founders were less dedicated to the idea than I am. In that case I would try to negotiate more equity from the beginning.