The Decathlon is anything BUT spongy on the elevator and downright touchy on the rudder! I have both planes you are referring to. The Decathlon is a handful to get off the ground but an amazing flyer in the air. The Cub, if you get one around 80" or so, will be pretty good handling on the ground and a super relaxing flyer in the air, and yes thats with the .52! The Cub will be the better of the two if you decide to add floats later on. The Cub will be a better plane to do touch and go's with. Decathlon is definitely faster, more agile, and more aerobatic. Neither of these planes like to be horsed off the ground before they have built enough lift to support flight and if you do so they both will reward you with tip stalls and major repairs. I enjoy the Cub on fairly calm days and enjoy doing scale like take offs and landings and practicing with. Slow flight is it's specialty and it flys with the typical tail high attitude.
The Decathlon requires your attention the whole time but it rewards you with great snaps, knife edge flight, low inverted passes, speed, etc. Two totally different planes!