I suppose ultimately the thing to test is application performance, (assuming you don't care too much about disk space). Because it depends on the access pattern

I suppose ultimately the thing to test is application performance, (assuming you don't care too much about disk space). Because it depends on the access pattern. If reading and writing contiguously, then large record sizes (even if unaligned) with high compression ratio might be fastest. but if it's more weighted to highly randomised, then the larger ZFS record sizes might actually cause read and write amplification and a lower throughput even if the overall on-disk size is smaller (assuming it doesn't all fit in memory in which case this is all moot). Another new thing that's possible with innoDB these days is that you can actually change the default 16k page size, i.e you could align innoDB to your preferred ZFS recordsize if that makes sense for your application.