Everything between yourself and the output of speakers is affecting the sound in any way. Sometimes, very subtly, sometimes dramatically. Picks (or plectros) are some of those things that a guitarist is often unconsidered by the guitarist as something that can affect his sound.
In fact, I am quite sure I bought a wide variety of picks along my life, of different makers and with different characteristic and that, maybe at some point of time, I had my own preferences but, I really forgot it.
One day, I saw a thread in Seymour Duncan, discussing about pics and, it took my attention.
Can a pick be so determining in my playing?.
Nowadays, we have a huge offer of different makers, models, with very different shapes, materials, stiffness. Do they make any difference?.
Nowadays, picks are made of a bunch of different materials, as Cellulose, Delrin, Ultex, Nylon, Bone, Wood, Copper, Aluminium, Shell, to name a few.
Material affects to the touch and, interacts directly with the string, transmitting our movements in different ways. Some materials seem to have some grip and, seem to hijack the string (for milliseconds, if you want) while you are playing. Other materials seem to release strings easily, allowing you smoother pick down/ pick up stuff. By example, I've got a wooden pick that seems to hijack the string, making it really difficult to do something speedy there. Something similar happens with a bull-horn pick I've got. Dunlop's Tortex and Nylon picks have this effect in a lesser degree but, in higher degrees that same picks of other materials.
So, they are affecting to how fluid is your playing.
Materials are also affecting the attack and sustain phases of your sound. By example, Nylon has a sweet attack and, the resulting sound is somewhat more mitigated; this can be a wanted thing for certain songs but, I personally don't like the resulting sound. I've got a copper pick with a really hard attack, even making the strings jumping as crazy, even altering the pitch of those. It gives a hard bite, adding some metallic high end to the sound. I know Brian May plays with a penny coin of copper but, I personally cannot stand the results. The copper pick, together with the bull-horn pick are the ones with the harder attack and bite.
In my memory, Cellulose or Shell picks were working better but, I've got none to test and, maybe, they are not of my taste, nowadays. Who knows!.
Personally, I like more picks made of synthetic materials, with a very well sanded surface, were you can feel your finger sliding smoothly on its surface. That usually corresponds to a pick that easily releases the string.
Something else to consider about materials: some are really soft and weak and, therefore, last less time. Also pick' shape will be lost earlier in time.
This little detail affects a lot on how do you play. If it is thin enough, it seems to get trapped between strings, when jumping from one to the next one and, this is independent on of which material it was made.
If it is stiff enough, the strings are attacked so hard that, they seem to jump out of the guitar's nut.
It seems that, the more stiffer the pick is, the easier is to play speedy riffs but, as always, the stiffness that works for some people cannot be the one you need.
I am finding also that certain stiffness are more valid to play a certain type of music so, even each musical style can have a stiffness range that better suits its needs, depending on what are you after (bite, attack, smoothness, warm...).
You can think that Shape is just an aesthetic thing but, it isn't in any single way.
Some of the shapes are a real mess to my playing technique. Big shapes are specially bad for me, specially those big triangular picks. The bigger they go, the bad for my own needs.
By example, the Dunlop Stubby Triangle (purple), with an stiffness of 2.0 is made of a material that I like but, I cannot stand the shape, it's a real mess. The point of the pick stands so far away my finger that is really difficult to get some good overharmonic, by example.
One more example is one of those V-Picks (expensive as hell). I've got one Shredder, with a perfect triangle shape. The tree points are well finished, with a very sharp profile. It's a very rigid pick and, with excessive attack to my taste (stiffness 3.0).
I usually prefer Tear-Drop shaped picks and, the smaller the best. I like them with a softer point, not so sharped as the ones of V-Picks, by example.
I've found that the shape named "stiffo" by Dunlop is the one that best suits my needs.
The Dunlop Jazz III Stiffo is perfect in shape but, I don't like the material so much. Maybe, same shape with the material used for the Stubby Triangle or the one used in V-Pickup would be my natural election.
The Jazz III seems less finished, with its margins not so well sanded as the Stubby or V-Picks or, even the Ultex ones by Dunlop but, this pick has a nice grip and its the most similar to play without a pick.
Currently, I am using the Jazz III Ultex, that convinces me more than the traditional Jazz III.
To choose the right pick for everyone isn't so easy as you can think. It's incredible how much you can improve your playing technique with the right pick and, this is one of the cheapest "mods" you can buy.
Lot of people is spending lot of money trying to sound better and focusing in expensive things that add way little to the sound than a simple change of pick.
By example, to upgrade your caps from ceramic disk to sprage orange drop has a ridiculous impact in your sound, compared to the effect that a different pick will bring to you.
I've personally reached to the conclusion that the kind of picks I like more are made of very well polished synthetic material, with an small tear drop shape, with a not so excessive sharp point and, with an stiffness between 1.0 and 2.0.
The best pick I've tried up to now (for my needs!) is the Dunlop Jazz III Ultex.