I'm impressed with the fuel economy of my 74 with the new carb. It seems to barely sip fuel. I also like the hex socket, which allows me to adjust the mixture with a ball driver from a comfortable distance. The new carb behaves well - no problems whatsoever. But I have no experience with the MkX.
I finally got my engine quieted down enough to fly at my club. It took a combination of the Fox Quiet Muffler from Hobbsy and a 14x8 APC prop. I wish Fox would get back to producing engines.