The first Leicaflex has the "aerial image" you describe, the SL & SL2 are quite different.

The SL has very fine microprisms over the entire surface (a bit similar to a Nikon H screen), which makes focusing extremely easy anywhere in the field, even the corners.
The SL2 has a more "traditional" looking focusing screen, but still one of the very best I've ever seen for brightness, contrast and the image snapping into focus.
I do slightly prefer the SL's screen, but the SL2 can use some of my favorite lenses which the SL can't (19mm II, 15mm).