I have both, and the 9 has given 110%. I'm at just over 1300 rounds with it, and only one jam, and that occured when the slide released during a magazine reload, it fed the round just a little too high and caught in the ejection port.
The .40, has been a little imperfect, but whether it is the ammo, or the recoil springs, i'm not so sure. It only has about 700 rounds through it, and at first, it was occasionally failing to go into full battery. The slide would hang about a quarter inch. This wasnt happening all the time, but enough to be annoying. Now, this last weekend, I had a dozen fail-to-fires. No more out of battery, just fail-to-fire. The case was being struck by the pin, but never in the center, always around the edge. This was while using Aguila 180 gr FMJ/FP. In fact, Aguila is just about all its been fed, except for the first two boxes, which i don't recall what they were. But anyways, its been suggested this problem is in the ammo, and the only other answer would be, in my humble and UNeducated opinion, would be the recoil spring is weak.
Overall, the .40 has been okay but the 9 is my favorite. In comparison to a Glock 19, the recoil is lighter in the Steyr. The sights though, take some getting used to.