it all depends on what you want, low-end, mid-range or top-end. the PC set will give you top-end and overrev, they only have 2 kinds of pipes, but theyre pretty close in power output. the FMF Fatty and Shorty silencer is a great combo for low-end. just tell us what you want, no one can tell you what is best without knowing what youre looking for.
you can get them straight from PC for $350, thats when you order a Platinum pipe and R-304 Shorty Stainless silencer, thats the best combo from PC if you want power.
i got the platinum and r304.. she aint quiet but not rediculously loud... most of the power is like mid to high, but it's not like theres 0 power down low either.
A shorty delivers more bottom end whereas the Regular delivers more top end. Personal preference and riding style is what determines whether you want a shorty or not.