On paper I would prefer ZF versions, as I shoot both Canon and Sony and the aperture ring allow me to used them both on Sony with the MC-11 and AF them through TAP, while with ZE lenses is a strictly MC-11 manual focus affair.
Two factors are nonetheless usually in favor of opting for a ZE version instead:
- for shorter focal lengths they tend to be shorter, i.e. more compact
- they usually cost less, in some instances quite a bit, like for example the Distagon 35 F2, which I consistently see selling for about 200 bucks more in the ZF/ZF.2 version (of course potential resale value is also higher). I've just bought a ZE on eBay for that very reason.
