To answer the question of performance of a 92mm vs. an 80mm on a heatsink, there can be MANY factors saying what will perform better than the other.
A larger fan tends to move more air for its RPM and noise. A smaller fan tends to spin faster and move less air for its RPM and noise, however, since it spins faster it has a higher static pressure. Static pressure is very useful in terms of lowering temperatures when ramming air through something or making it go some place it does not want to go very easily, like through a heatsink.
True, the 92mm Tornado moves more air, but in a case like this, it could be an issue of static pressure more than total airflow.
Also, what size the heatsink is designed for. A 92mm might have a larger deadspot, worsening cooling performance with most heatsinks excluding something like the SI-97 that relies only on heatpipes and its fins are not attached to the base, where a deadspot does not matter.
So, the best thing is trial and error.
In general, sometimes the advantages of a larger fan outweigh the disadvantages and you can get better performance with less noise by using a larger fan. Sometimes it could be the opposite as well.