I'm told it's about the same.
The break in period is the maker's way of keeping a user from destroying it quickly. A good dealer will do part of the break in when they prep and mount the motor. Specifically the idling part of it. From there, it's just a matter of not running wide open for long periods. You can go full throttle, just vary your speeds up and down.
If there is a problem with the motor, you'll find out within the first hour or so usually. And a lot of times, when a good dealer is doing the break in (I do it in a horse trough just idling), if there were a problem, the dealer will fix it before you ever knew about it. I work with Yamaha's and rarely see any kind of problem with them-even the 40/30's. They're very popular out here, last year the place I work for sold about a dozen or so jets, couple of them replacing Merc's. Rest were new boat installs, river boat, already set up for the 40/30.