I was all set to endorse the .52, because I think training is best accomplished with a little less power than is usually used.
Then you said,
...and later have power to spare for some more acrobatic plane.
If you're buying an engine for a future aerobatic warbird, I think the minimum is probably that .70 fourstroke.
But I still recommend the smaller engine for the plane you learn on.
Just my opinion. Good luck,
Dave Olson