alchemist: i own an hr-2 and ps-5, and i have a lot of friends who use ps-3 and/or whammy, and i have to say that the ps-5 is a piece of crap. the hr-2 and ps-3 are polyphonic on octave settings, plus the synthetic generated tones are a lot more pleasant than the ps-5 or ps-2.
the main reason i use the hr-2 over a ps-3 is that with the 2 generated tones, you can both pitch-shift and use a detune chorus at the same time, which is what i do to achieve simple organ- or synth-type sounds. the ps-3 (i believe) tracks slightly better than the hr-2 on non-octave settings, while the ps-2 doesn't track well at all. the ps-5 tracks well but doesnt sound good, and it gets very confused with intervals (especially when you're pitch-shifting thirds or sixths).