I've listed them, but again:

 * You can read the class declaration; what it has, and does, at a glance.

 * Function's don't have a few extra tab's of white space by default. This means you can more easily understand the flow of code within your class.

 * Your code uses less horizontal space.

 * I find it easier to review commit's in diff's, since I can clearly see separation between API changes, and function implementation changes.

I find it much easier to detect the difference between 0, 1 and 2 tabs deep, than 2, 3 and 4 tab's deep.

I believe there's an exponential falloff to your precision wrt estimating tab depth the deeper it gets. This makes the code less easy to follow; "Am in inside a loop, an if block, or a local function? What depth is the outer scope of the function anyway?" while skimming through code.