The main benefit of Apache 2.0 is that it includes a patent grant as well. Right now, LLVM relies on a custom "developer agreement" for anyone who contributes code that includes a grant of patent rights, but it's kind of vague and fuzzy and so makes it hard for some people to contribute, and the license itself doesn't actually mention patents at all:
http://lists.llvm.org/pipermail/llvm-dev/2015-October/091536...
Theo objects to any license that applies more restrictions than the original BSD license. OpenBSD makes an exception for GPLv2 licensed utilities that have been traditionally shipped with BSDs that there's not a good replacement for, but has stopped upgrading things that have moved to GPLv3 and apparently objects to the Apache license as well.