I've owned several Sigs and H&Ks over the years... now I don't own any. Personally, I can control my shots in quicker succession better with Glocks, 1911s or even more recently, a Steyr.
Cost isn't a significant reason you see glocks in competition IMO, otherwise you wouldn't see so many 1911s, 2011, CZ platforms etc because those aren't that cheap either. It's honestly just a better platform to shoot faster shots on target for those particular people. The bore axis makes a significant difference for me, again, when practicing shots on target in quick succession. This is what self defense is all about IMO and it just happens to score points in competition aswell.
FWIW, my Styer M40 is by far the most controllable .40 I've ever owned, including a full size .40 1911. I've owned a Sig P226 and P229 in .40 and neither came close.
I never heard of a Steyr M40 before, so I googled it. That's one crazy lookin' pistola