Not sure if it is safer, but never heard people say it is worse.

However, what I can tell you from personal experience is, it is heck a lot harder to use. Correct locking technique says you are suppose to lock the frame and the rear wheel to the bike rack with a lock. Depending on the rack shape/how compact the mini lock is, this can a feat to achieve. I have the kryptonite ny fahgettaboudit mini u-lock.