AApoints, Kingdom of SkyFollow

You can put points in either tree as soon as you hit lvl 10 and have both expansions.

As to what is preferable, I'ld say first the KoS tree myself actually.

Well, the EOF tree more or less improves existing spells and abilities. Some will have their casting time reduced, others their costs of casting, other spells will be increased in function. Those kind of things, when putting enough points in one of the three subtrees, you can get access to one of the three special abilities at the bottom.

But in general it exists to boost your existing spells.

The KoS tree actually adds new spells and abilities. First line is a simple passive one (5% speed increase for my monk, out of combat), the second line improves stats: stamina, agility, strength, wisdom, intellect. Starting from the third line, you will get new abilities. The last line is the special ability, not always as great as the cost for getting it would imply though. Although they do add a lot to combat, for instance my crane flock lets me fight for 16 seconds with double attacks and a speed increase.

However, with only 50 points to spend in either tree, you can't fill out everything. For instance, you can only get two endline abilities in the KoS tree. Which should be enough to get one heck of a boost in combat though, don't get me wrong.

The KoS tree for me seems to affect the combat more and faster than the EOF tree.