Well, it looks like the plugin is magnitudes faster.
This are some results you can see with the sample project:
String Created: 1.048.500 bytes
RegExMBS: 8.120 microsecs, 500 found
RegEx: 317.797 microsecs, 500 found
String Created: 10.485.000 bytes
RegExMBS: 77.930 microsecs, 5.000 found
RegEx: 33.953.951 microsecs, 5.000 found
Tested in RS 2012r2.1 with 13.1 MBS Plugins.
Even with sampling on Mac OS X we can't see what the RegEx class does with all the CPU time. Maybe they simply rebuild the regular expression every time they do a search. We'll see. If you are interested, subscribe the Feedback case 24836. For now you can simply use our plugin if you need speed
See test project: regex_speed_test.rbp.zip