It really depends on what you want in a plane. Both of these are terrific models. The Rascal has that great, classic look about it, and your 52 4stroke is about perfect for it. The 4* 40 has a bit broader flight envelope, more aerobatic and still easy flying. Your 52 will fly it well, but you might want a bit more power for some of the more aggressive maneuvers if that is your flying style. The Rascal would not benefit a lot from more power, as it doesn't lend itself to aggressive flying.

Either way, you won't go wrong.