Diffusion models are harder to train than flow matching because their velocity field depends on the density.

“the Fokker-Planck equation reduces back down to having a very specific um velocity field. And if you look at this velocity field, you end up doing so you end up realising two things. One is of course like there's a fundamental connection between these two methods. The second thing is you can see why diffusion models are kind of iffy to train or uh more so than diffusion. Because if you look at the velocity field, the velocity field actually depends on the density.”