I saw a speed comparison of a bunch of different awks here, some months ago. mawk was the only clear winner. But it's too quirky to use for everything, it breaks some normal-looking scripts for reasons I don't quite understand.
Actually
crashing is a new one, though. That's an actual bug. Maybe you can fix that by getting a newer version of mawk.
GNU awk -- and the GNU tools in general -- are nice because they don't have line length limits. Many commercial nawks and seds have limits of 1000 or 2000 characters per line, and many threads here are about how to kludge around that problem.
In the end, though, my brain divides awk into two realms: "GNU Awk", and "Where'd mktime() go".