Use spaces because everything else is worse unless used with extreme caution, not because spaces are awesome. Perfectly tab-formatted code, in an environment where you know the tab stops will be the same for everyone, is probably the best case--but the instant someone grabs a code snippet and tosses it in an email message (5-space tabs...the horror!) or changes their settings, all that effort to line things up is not only for naught, it's actively harmful to reading the code.
It's not that spaces are better, it's that they're least awful when awfulness happens (and it will.) Other people have to read your code, if you're at all serious about programming, and it's not excusable, nor effective to demand they conform to your tab stops. So don't use them.
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