To major things that determine if you can get a long, hard stool to flush:
- no sharp bends in the pathway
- a large diameter path
If you look at the side of many supposedly well respected company's toilets, you'll see that the path of the outlet is not particularly smooth and many of them try to turn a 90-degree, sharp corner at their exit. Everything can work okay with 'normal' people's dumps, but not when it is hard and long. There, the above factors are the prime asset that allows them to perform.
A pressure assisted toilet can work sometimes since that high pressure jet can literally tear apart some of those stools which means they are no longer 'long', but are still hard, and have a good chance of being able to get by the curves. That high speed jet can cause splashes and leave smaller particles floating in the bowl sometimes, meaning you may want to flush again to clear things. Plus, they're noisy, not necessarily something you might want to use in the middle of the night.