The default map marker is the traditional "circle with an x". This marker is very large and if you need several markers in a small area, the map will be cluttered. the small dot is much better.

Since scrolling through the multitude of available markers is a bit tedious in the middle of a multiplayer match, the smaller and inobstrusive markers should appear first, larger markers which are more likely to be used in mission building or during the preparation phase of a match could be a little lower in the list because using them is less time critical.

If possible it might be a good idea to allow players to arrange the markers in a way they find practical.