I think the physical and chemical properties of magnetic nanoparticles largely depend on the synthesis method and chemical structure of your product . In most cases the particles range from 20 to 100 nm in size  may prefer to this kind of reaction. 

In coupling reaction CuFe2O4 is mostly useful and strong magnetic properties.

If you used nitrate salt of precursors than you will get some acidic side on ferrite and its acts as lewis acid. it will be used in acid catalysed reaction.

If you want to use as a support then used Fe3O4. You can desgin the magnetic seperable catalyst. But If  you want to use as a catalyst then CuFe2O4 is better  catalyst in organic synthesis.

Its depend on what reaction you chose, though cobalt and copper related reactions will work on well defined CoFe2O4 and CuFe2O4. 

Please refer following review, it will help a lot...

Article Nano-Magnetite (Fe3O4) as a Support for Recyclable Catalysts...

I think CuFe2O4

CuFe2O4 is better catalyst in organic synthesis like coupling reaction and  mannich type multicomponent reaction.