One of the many advantages of using metal bases on my figures and magnets on my movement trays is the ability to create markers that "stick" to the unit. Not only can I remove individual figures for casualties, I can easily mark the unit with a marker that sticks with that unit when I move it.
For example, in my rules, I need to be able to mark units as belonging to divisions on the board. I created different colored division counters and mounted them on 1/2" strip magnets. Units of the same division have the same color. Units not in their division suffer penalties. Since it behooves the player to keep his divisions together, the colored markers make it easy to keep track of this.