I wasn't around when "pip search" was written, but I think we need to use `pkg_resources` for comparisons across the board in pip for consistency.

http://pythonhosted.org/distribute/pkg_resources.html#parsing-utilities

`pkg_resources.parse_version('1.2')  <   pkg_resources.parse_version('1.3')`

in `pip list` the comparisons happen in the context of Distribution objects, and the sortable parsed version is available via the `parsed_version` attribute.