They have a slightly different prop - the "SP" runs at a slightly higher
RPM, and as a result has a higher HP rating. You will not get any better
cruise out of it though. You may notice a "slightly" better climb
performance in the "SP" but basically, having flown both quite a bit, I
don't detect much difference - they fly the same.

Take a look at the panel. If you're looking into slightly older "R's" you
will likely find a King KLN89 type GPS, and an ADF. The slightly newer
"SP" series typically had Garmins, or KLN 94's and KMD-550 MFD's and they
eliminated the ADF (these are not hard and fast rules - you can find
either plane with either configuration, not to metnion the newer
G-1000's, but these are generalities). So if you want an ADF, you're more
likely to find it in an "R", and if you want a large, moving map display
you will be more likely to find it in an "SP".

Also, take a look at the W/B sheet. Those extra horsepower don't
translate to much preceptable extra performance, but they allow a
somewhat higher useful load. Depending on your needs, that could be an
appreciable difference!

GF