I'm looking into getting myself a DOF adapter, probably the GT35pro Elite because it fits into my budget, but I've never really had to buy lenses before. What kind of mount would I benefit most from, Nikon or Canon? Basically what I want to know is whether it will be easier/better/cheaper to go with one rather than the other, in the long run.

If you intend to mix and match lens brands, then the Canon EOS mount might be handier because you can fit a Nikon adaptor to it but you cannot cheaply put Canon lenses to a Nikon mount via an adaptor because the Nikon flange face is furthur from the focal plane.

Thanks for the reply. That's exactly the type of answer I was looking for :D

There is one small potential but irritating problem with a Nikon lens to Canon EOS adaptor. There are two mount joints which means that they need to be good otherwise there can be flexing on the joints which makes problems when using a follow-focus.

I'd go with Nikon. It's easier to find them with a manual aperature. EOS lenses will require you to get another device to set your exposure. I've had a set of manual nikon primes for a couple years with my letus and have been very happy.