I'm not exactly sure what measurement you are looking for, but lets assume it has to do with how far the regulator sticks out from the valve towards the back of your head. If that's what you're after, there would be no appreciable difference between yoke and DIN. The 300bar DIN has two extra threads on it, so using it with a 200bar convertible valve means it sticks out more maybe 4mm or so as opposed to the same reg in a 300bar valve. If you are trying to compare how far towards your head the same regulator, fitted with yoke as opposed to 300bar DIN, on the same convertible valve ( those are all 200bar) would be, the answer is not enough to worry about; maybe the 300bar DIN sticks out a bit more due to those extra 2 threads.
Using a 300bar DIN regulator with a spin on adapter on a yoke valve pushes the regulator about an inch, maybe a little more, closer to your head. That is appreciable. For me it would be totally unacceptable to do on a regular basis.
But there's another issue which you haven't mentioned, actually two issues. One is that if you are diving with yoke tanks primarily, you should definitely get a yoke reg. Once you put the DIN/yoke spin on adapter, you have immediately cancelled the advantages of DIN. A DIN reg on a yoke tank with the adapter is the most trouble-prone connection you can have. The other issue is with the convertible valves in rental situations, like in the Caribbean. Those inserts tend to stay installed for a long time, and the threads are not protected from saltwater, so they get very corroded. I've seen them strip a few times on boats where the DM is trying to remove it with a rusty allen key so that a customer can use a DIN reg. That make the tank useless until the valve is serviced or replaced. Maybe they're starting to figure out that you have to remove those inserts after salt water dives, but I wouldn't count on it.
So if this whole conversation is about using DIN regs vs yoke regs with yoke tanks, it's a much better idea to get a yoke reg. If you are diving primarily with DIN tanks (your own, that are maintained) and you need to occasionally use a yoke tank, then fine, that's what the adapters are for.
Sorry for the long post, hope it's helpful.