I also have a Super Program, but I've tried out a few ME supers. They both handle about the same, are about the same size and weight, and they both use up/down buttons to set shutter speed. So the main difference is in features, and the SP just
whips the ME super.
In addition to what Mo mentions above, the SP has a digital viewfinder readout with shutter speed, aperture (in Tv and P modes), +/-3 stops exposure (in M mode), flash ready/OK, and exposure comp warning - it's a better VF than in the later autofocus SF1/SF10 models. The TTL flash is compatible with the current Pentax flash models, too. It even has a little window that tells you that the film is advancing properly. My only complaint is that I think the shutter (or maybe the mirror) is a bit loud - it's louder than my ZX-5n - but I think it's exactly the same shutter as the ME super, so it probably sounds the same. It was cutting-edge stuff when it came out in 1984, and it's still not too shabby.
I think you should get the Super Program. I had been thinking about selling mine, but I may have just talked myself into keeping it!