I've had top tier players tell me to only use my arm and others tell me to only use my wrist when playing. This comes down to whether the picking arm is planted or is free to move while playing. I do believe if you observe other players they will fall into one of those two broad categories.
Nowadays I am solidly in the "wrist" category and I have my own arguments for why that is so. I realize a lot comes down to personal preference in sound but I'm curious what others think.
Chris Thile is a weird case because he's primarily using his wrist but he doesn't rest the hand on the bridge, which gives more of the impression he's using more arm. This to me bears a resemblance to Dave Apollon's style.
If you look closely though you'll see he keeps his arm planted on the side of the instrument. I've never met him but I've spoken with someone who has asked him about it, and he said he decided to float his hand to achieve more tone. Plus it's clear he has tons of mobility, which is something you lose when planting the hand.
Mostly wrist for this player.
Wrist mainly...YMMV
People seem to recommend mostly wrist. Same for guitar. Doc Watson was always considered an exception with his full-on arm style.
Is the use of wrist vs. arm perhaps a function of where people take their training, such as bluegrass vs. classical?
Monroe seems to have been wrist mostly. Lichtenberg seems to favor a combination of the two.
I use both - Mr. Miyagi might say this is why I'm not as successful as I'd like.
When I like how someone sounds, I watch what they're doing and try to copy, and when I like, it's usually mostly wrist. I think I'm more than 50% wrist, but when I really like what I'm hearing, the other guy is usually more like 95% wrist.
I use my wrist for tremolo and picking individual notes. Generally I use my arm when playing chords though
That said - even when using my wrist for tremolo or picking, it doesn't mean that my arm isn't involved and moving a little too. It's more that the primary motion is coming from the wrist.
Something I would recommend to keep in mind as well - Proper Technique is largely a group of techniques that work well for a large number of players. While generally there are merits to "proper" technique, it doesn't mean that technique is proper for you. Look at players like Chris Cerna who has horrible technique if you compare him to the "proper" but he's a fantastic player and it works for him. Michael Cleveland is similar for fiddle.
I was an arm learner, player, but am trying to convert to wrist.
