I'llswear on my guitar that you'll get more speed, and much much much much more endurance picking from the fore arm. I played from my wrist for 10yrs before switching my technique, and it's made all the difference in the world. It only makes sense, your forearm muscle is much bigger and more powefull then your wrist or fingers. Violin players have been using this technique for centuries, and we all know how fast they can play.
As for switching strings, try using directional crossovers, approach each string in the direction you are moving. If your playing down the neck (high E to low E) approach each str. with a up pick, and vice versa. I learned this technique off of Jimmy Bruno, you can see him explain it on his Hot Licks video No Nonsense Jazz Guitar.