Rearsets: Aftermarket rearsets are not only adjustable, but have better, and replacable parts in the event of a crash. The adjustability is a benefit, as most allow 1" up and 1" back, benefiting taller riders like myself.
Stock foot pegs, generally suck grip-wise, when compared to aftermarket parts. My Vortex pags grip 10x better than the stock ones. Also, their pegs are solid mount, not folding. Helps keep the side of the bike off the ground in a crash, as well.
Clip-ons: Aftermarket clip-ons are good for numerous reasons. They're lighter and in the event of a crash, their "tubes" (where you grab and controls go) are replacable, unlike stock units. They're adjustable as well, since some guys like a higher grip, or might want somthing wider for better control, and less tucked into the bike. If you use them on the street, vibration can be an issue. You can get aftermarket bar-ends for weight, or you can put your own weight in them. I added weight to another aftermarket set, and secured it with silocone. No more vibration than stock.
Oh.....It's on, Biotch.............