I prefer to use balanced delimiters for several reasons, not least of which is consistancy.

I'm with you on that one, but you could use curly brackets. That way your regexes wouldn't look like big character classes.

two statements rather than one seems like the most obvious case of premature optimisation

The OP specifically asked for an efficient way of doing this. I saw your capture and thought it was unnecessary.

I also think that your benchmark is flawed

Well I didn't type out the results by hand :P

Having said that, I've no idea how they would be affected by different data, but only the OP can do that properly, as we don't have a sample of the actual data to be proceessed.