The value of main stat to Crit is pretty much the same for all classes (~0.214), but the value of Det varies wildly based on the particular skill it is being applied to. Det for SMN is more along the lines of ~0.134, which when you consider how much of it you get on gear, makes it plainly inferior to Crit.

So, there is no straight forward answer, and it is going to vary from class to class based on skill potency and implementation.

A general statement could be made that Det is worse on low potency skills than it is on higher potency skills, which is why it comes out better for BLM than Crit, on a point for point basis.