speed.python.org has been updated to split out per-branch results for easier cross version comparisons, but looking at the performance repo suggests that the only 2.7 results currently reported are for the default UCS2 builds.
That isn't the way Linux distros typically ship Python: we/they specify the "--enable-unicode=ucs4" option when calling configure in order to get correct Unicode handling.
Not that long ago,
pyenv also switched to using wide builds for
manylinux1 wheel compatibility, and conda has similarly used wide
builds from the start for ABI compatibility with system Python
That means the current Python 2 benchmark results may be unrepresentative for anyone using a typical Linux build of CPython: the pay-off in reduced memory use and reduced data copying from Python 3's dynamic string representation is higher relative to Python 2 wide builds than it is relative to narrow builds, and we'd expect that to affect at least the benchmarks that manipulate text data.
Perhaps it would make sense to benchmark two different variants of the Python 2.7 branch, one with a wide build, and one with a narrow one?