A few years back I was having the same debate. Knowing my tendencies to drift between hobbies I decided a staged approach was in order. I bought the 10" Coote and figured that if I made enough knives to justify it I would later buy the KMG.
Now fast forwarding to the present. I have made approximately 100 knives and have not found a need to buy another grinder. I know some suggest a 2-wheel grinder a bit more difficult to flat grind on however I do not find it difficult at all. All of my knives have been flat ground except for a couple and I still have the end of my nose.
Personally, I would buy the coote and put the extra money into belts and other tools you will need. Once you start making, let your hobby pay for itself and when it can, buy a brand new KMG with all the extras. There is no doubt that the KMG is a beautiful piece of equipment worth every penny. For me, for now, I do not sell my knives and knife making has remained a very relaxing hobby. I think for any hobbiest, the Coote is way more than enough.
Best Regards
Dean