Any thoughts on the R screen?
I use an E - it's much like the R but with a fine matte spot in the middle; the R is specified for "lenses having maximum apertures from f 3.5 to f /5 6," as the central split-image prisms are flattened. I'm sure the R works with larger aperture lenses but the split image action isn't as optimum as it could be.
I like the 'P' for general 'snapshot' use. It's a set of crosshairs with a 45degree split-image prism.
With age I found my pictures started to come with sloping horizons. Not much of a problem with B&W but a real annoyance with slides and machine RA4 prints. I now have cross-hair or grid screens in all my cameras, with the exception of an N75 - but that has a grid of focus rectangles in the finder that work pretty well for squaring up the composition.
As for Beattie screens, I have one in a Hasselblad. A PITA in my opinion. Works well with the WL finder but goes dark with a chimney finder. The Nikon screens work with all the finders you can fit: prism, HP, WL, critical magnifier and action.