Pressure-assisted toilets really blast water through the bowl and out the trap, but they tend to be noisy. Look for toilets with the largest opening under the flapper and the tallest tanks. The faster the water enters the bowl and the higher it drops from, the more pressure you get. The S-shaped throat of the toilet should be glazed and as clear of ragged edges as possible. An unglazed trap is rough, and material does not slip as easily over the surface.
Ragged edges can catch paper and clog the trap.
The deeper the standing water in the bowl the better. It improves both the atmosphere and the flush. Most new homes are built on only a 5 percent margin for the builder. He's not going to upgrade the toilets and eat into his profits. The buyer has to do it.