Unfortunately people (customers, developers, hardward vendors) make
decisions on the basis of bang-for-buck. FreeBSD is consistently
underperforming on benchmarks. And regardless of real-world similarity,
the contrived benchmarks are the best that is used.
If clang (v3.4.1 on 10.3 Stable) really is the cause, then there should be
an option to use "whatever" will let the source perform at its best
and
reflect the stability that we have with FreeBSD.
We can criticise the test results or the test regime, but unless
knowledgable people respond publicly and/or in the phoronix forums, such as
https://www.phoronix.com/forums/forum/software/distributions/891660-benchmarks-2-bsds-vs-7-linux-distributions
Then this interpretation of reality will be fixed in decision-makers' minds
and consequently the uptake (and support) of FreeBSD.
As I recall Michael's testing regime has been consistently criticised (by
FreeBSD folks) since he started his website, unfortunately when someone is
making public statements and comparisons we really need to have a
relationship with them to ensure that FreeBSD's best position is put
forward.