I tested a (worn out) 30mm 2011 otk vs a 2013 32mm (2 races old) a few years back.
Both were setup exactly the same with the engine on the 30mm being 0.3 seconds faster.
The 30mm was faster but only a few tenths of a second, (0.7 fastest lap diff) if it wasn’t dead it would have been more for sure.
I liked the way the 32mm drove more, it was extremely direct/responsive compared to the 30mm. But that also made it harder to drive because you are balancing on finer margins.
In the notes of that day I kept describing it as “really sharp” to drive.
The 32mm couldn’t take kerbs at all compared to the 30mm, but the wear on the 30mm probably has had a huge impact on this
There were no big differences in terms of over/understeer or hopping.
Testing was done on mojo d5’s with a rotax senior engines