I was NEVER TABS until someone else asked me to consider why, and now we use tabs for that reason: everyone can have their preferred width.
When you mix tabs and spaces there's no way to get alignment correct. Indentation is fine, if that's all you ever use them for, but human behavior is non-deterministic and unenforceable, making for completely hosed up source when tabs are used for anything other than pure indentation. E.g., if you put a tab in for alignment, when you should have used spaces, your source file is hosed up.
Add on to that that many IDEs, editors, and build tool/tool hooks aren't smart enough to know when something is being indented vs. aligned, it's essentially impossible.
Until editors align properly with a single tab char (something even a word processor will not do) then spaces are the right way.
If sometime in the future they device some new formatting standard it would likely supplant and deprecate tabs, but spaces I believe would always be a fallback option.
if you work on a project with multiple collaborators pick one (i.e. tabs or spaces) and stick with it (i.e. enforce it during code reviews).
I personally use tabs but those get expanded to 4 spaces by Vim. Works for me!