Got both those units. Much prefer the Satmap for navigational duties, and use the Garmin for recording trips or navigating when I kinda know where I am as it is small, neat.
Mount is secure for both and Satmap put a thick rubber band type thing to stop mine rattling. Mount is expensive for what it is, but good.
If you can get the Satmap on the stem it is fine. Rather clunky on the bars though.