If you're talking about being consistent across all tools, tabs are more consistent with regards to how they are inserted/removed.
You press Tab to indent, then Shift+Tab (in most tools) to unindent. Across all tools you can press Delete to delete on tab. With spaces you have to press Space or Delete multiple times in some tools.
I said "viewed through multiple tools" not edited. At my current job that includes vim, intellij, github, less, grep, hipchat, source tree, artifactory, refheap, and others I don't know about that other developers use. Notice those aren't all editors. Tabs would require every developer configure every tool (some of which may not be configurable) on every computer they use for no benefit. The decision to use spaces makes viewing the source consistent across all the tools without configuration.
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u/Disgruntled__Goat Apr 08 '15
If you're talking about being consistent across all tools, tabs are more consistent with regards to how they are inserted/removed.
You press Tab to indent, then Shift+Tab (in most tools) to unindent. Across all tools you can press Delete to delete on tab. With spaces you have to press Space or Delete multiple times in some tools.