Ahoy!
The Min AF 300/2.8 APO was the first model and was superseded by the APO HS G which has focus hold buttons on the barrel and a slightly faster AF motor by around 33%, otherwise the optics are the
same, and I owned both models, but you can't tell the speed difference and the focus hold buttons on the APO HS G are rarely (if ever) used.
You would be best advise to go to
www.dyxum.com and research the lenses section where you can read all the tech specs, user 'reviews' and see image samples.
Let me know if there's anything else you need to know.
Pirate!