Skeptic- Interesting that you want a comparison between the 252 and Missile.
When I decided to upgrade from my 1967 F, I looked at Older Ovations which were out of my price range, M20S Eagles to then upgrade, slim pickings at the time, the 252 (my initial favoriate), and then the Missile, which was mainly an afterthought.
After looking at a few 252's and flying a Missile, I did the comparison, and yes, the Missile does burn more per hour. With my type of flying though, to make the 252 work, I'd have to go up into oxygen territory, and that's not my mission at this time. The Missile outperforms the 252 below 10,000, and outperforms early Ovations as well (weight vs power). The Missile and Rocket conversions are a big reason the factory started producing the TLS/Bravo and Ovation.
I decided I didn't need the altitude of the 252, and I was worried about the turbo. As many people have mentioned, once you go turbo, it's hard to go back. I decided for the type of flying I do, which is almost a 50/50 mix of cross country and local fun flying, I figured I'd go with the Missile. Plus, the Missiles I looked at were very well taken care of birds vs the 252's I looked at. I purchased a less expnsive bird both now and at overhaul with no turbo to worry about. That being said, boy is the 252 a heck of an airplane. Parker's 252 has been converted to the Encore, higher useful load, better brakes, and an additional 10 HP. I'm not sure if every 252 can be converted come overhaul time or just certain aircraft built after a certain point.
My choice in upgrade came down to the 252 or the Missile in the end. The reason I decided not to go the M20J from the M20F is I figured to spend that much more for 10 knots . . . it just didn't make sense at the time. At this time however, I do understand the extra differences of the J including a much better avionics package. The panel and avionics will be a huge step up for anyone coming out of a C,E, or F to a J,K,M,R,TN. My avionics in the F were fine. However, they are no comparison to even many of the factory avionics stil in my Missile (along with the added updates).