I haven't tried them to compare, but of all the buds I have tried I prefer the PK3, I even prefer the PK3's over the Shure E2Cs I had, despite the poor isoliation since hte PK3 is a bud, they're sound blows the Shures out the window. This is a $40 bud vs $80 IEMs.
Edit: I will see if I can do some listening with iBuds and PK3s tonight.
What sort of setup have you got? I am into my Bass as well, I like the Super Fi 3's for $50, they are fantastic, take a while to get used to the fit, but have great isolation and thumping bass

(note I do use an amp).