Putting it in the Governor's hands gives an awful lot of power to whoever's doing that job at the moment (it won't always be Dayton -- or even a Dem).
The 2/3 vote should be a little more consistent.
Generally, I don't think these ballot amendments are a good idea. They allow demagogues to flood the airwaves with propaganda and bypass the normal legislative process. Worse, they don't change laws, they change the constitution.
Thankfully, neither one passed this time, but I'd be happier if it were almost impossible to do this at all.