Tabs for indentation, spaces for alignment
I started using spaces for indentation just because I worked with people who did that. I kind of forgot I was even doing it because vim's auto-indent did a lot of the work, but after some time I realized spaces don't make sense.
The familiar arguments for tabs:
* Clean mapping between the concept of scope depth to a single character * Configurable display of indentation width, everyone can see what they want
Tabs have problems only when people use them for alignment, which breaks when tabwidth is changed.
Actually can someone try to change my mind? I know tabs-vs-spaces is an eternal war, yet I feel the problem is completely solved, hence I must be ignorant of the counter arguments.
(The only thing more logical than using tabs might be using no whitespace at all and having the editor determine presentation. But that wouldn't work well with line-oriented tools.)
The former is a pre-formatted fixed-width character document that can only be viewed one way.
The latter is a document which is easily processed; editors should show the intended logical representation of the information according to user preferences for conveying such meanings (though for terminal compatibility they often default to either 8 or 4 fixed width spaces in less powerful editors; still the meaning is conveyed clearly).