Dan, I jumped into the DSLR world about a year ago with some dated experience with 35mm film also. I chose a K20D and that is still my only DSLR so far. I started with a couple inexpensive-vintage-manual focus lenses and still mostly shoot primes, that seems to be a preference that carried over from my film days. The K20D is a fine camera and even though it is about 8 year old technology, it is a great performer.
So I don't own a K200D, but a general difference between the K20D and the K200D is that the K20D was a "flagship" Pentax model with some more advanced features and more of an "enthusiast" camera. A few of these are 2 control wheels instead of 1, a number of more advanced shooting modes, a pentaprism viewfinder instead of pentamirror, higher ISO range, etc. I also see that the K200D used a CCD sensor and the K20D uses CMOS (others can speak to this issue better than I can, not sure one is better than the other just different). You might look at this comparison, I put the K200D, the K20D and the K10D in but you can change these to any models you want to compare:
Pentax K20D vs. Pentax K200D vs. Pentax K10D - Pentax Camera Comparison - PentaxForums.com
Anyway you will get more input and advice from others as well. Good luck with your decision and welcome to the Pentax Forums.
---------- Post added 10-06-16 at 09:41 PM ----------
Another informative resource on this Forum is the Pentax Camera Reviews:
Pentax K-mount DSLRs - Pentax Pentax Digital Cameras - Pentax Camera Reviews and Specifications