A wrist mount would be nice.

I was checking out the Garmin and I discovered that the 405 is made smaller, and better for smaller wrists. The Garmin customer support person told me that the only significant difference between the 405 and 305 is that the 405 is smaller showing only 3 data fields as opposed to 4 on the 305. The 405 is styled more like the size of a normal watch. It also has a shorter battery life than the 305.