There are TONS of different fret wires. I have about a five foot wide section of wall about ten feet high which has nothing but coils of Martin Fret wire, which all has pretty close to the same size bead, but with different sized tangs. And then I have close to thirty other different styles of fret wire. You will excuse me if I don't go real in depth on each one, but instead give some generalities. And always remember that YMMV.
For MOST players, tall frets help them play faster, as your fingers don't touch the fingerboard, which means less friction. You also can use less pressure when you play, again because you are not touching the fingerboard, so it is easier to make the string hit the fret cleanly. Tall frets make bending and vibrato easier, again because you are not touching the fingerboard. However, until you learn what your touch needs to be on them, tall frets can cause intonation problems and can result in hand injuries (if you are used to feeling the fingerboard when you play, and you keep pushing until you feel it, you are bending the string, and pushing too damn hard. Very bad for your hands.) Also, tall frets can feel "bumpy," and make slides almost "quantized" sounding, if you get my drift.
Shorter frets are much more forgiving, and they don't have the bumpiness, but they do require more pressure to get the note to fret cleanly. But if you like to feel the fingerboard, you want short frets. Intonation is usually easier, as you are less likely to over stretch the string when you fret.
Narrow frets have no use that I can see except the feel. Also, if the fret is too wide, it is hard to dress it to a reasonable point contact, which is bad for intonation, but that is only ever an issue on short frets. Narrow frets also emphasize the whole bumpiness thing. I don't get the appeal of tall and narrow, but whatever, some guys like them.
Wide frets make a big difference in reducing the bumpiness. On shorter frets, they probably cause a little intonation problems, but then there are not a lot of short wide frets being used (the Gibson Fretless Wonders being an exception). Those Fretless Wonders have just ridiculously low and wide frets, and I don't really get how anyone can play them, but whatever.
Most of the really great players I know like really big frets, both tall and wide. Among those guys, Dunlop 6100 is really popular, and that stuff is HUGE. Too big for me. I like Dunlop 6150 more than anything, myself. 6150 is probably the most popular fret wire for electric guitars, though I don't know many guys who like it for acoustics (a few though, and one of the best acoustic players I know gets all his guitar refreted with 6100 - and his guitars are all old and expensive). And of course, one of our favorite customers, both as a player and a guy, HATES big frets. He talked with all these other guys who convinced him to get big frets on one of his guitars (a $350-400 job) and came back two days later to get it refreted again he hated it so much, for another $350-400. As I said, YMMV.
One other thing to keep in mind; I don't for a second buy the idea that small frets wear faster, but there is more material in big frets, so you can get more fret dresses out of big frets than you can with small frets. This is a issue to bear in mind as a dress is $125-150 and a refret is $350-500 (unless you are a one of these dips who want to keep your Gibson binding nibs, in which case you are looking at least $800 because of all the extra work involved).
And then there is the material issue. For a long time frets were either brass (in which case your guitar was really fucking cheap), or either 15% or 18% Nickel-silver (which has no silver in it at all). 18% is harder, and is usually used for all steel string guitar frets, with 15% being primarily used for nylon strings and mandolins, as it is difficult to get the harder 18% as small as mando frets usually are). In recent years, however, there has been some move towards stainless steel frets. This started in popular conciseness with the Parker Fly's, and now there is a limited number of sizes of fret wire available in stainless. Basically, it is available in Martin sized wire and 6150 sized wire. Expect an upcharge on the labor of at least $100-150 for this stuff, as it is extremely hard, which means it does not like to seat very well and it is very time consuming to file. Also, we can't use our normal fret cutting tools with stainless wire because it chips the cutting edges, which means we need to carefully file it flush, which sucks.
All the bad points aside, though, stainless wire IS much harder, so it lasts a lot longer. I have customers who get complete refrets once a year (not because they couldn't get a fret dress, but because they do not like the feel of the shorter frets. They want their frets as tall as possible). Most players don't need fret work that often, even with nickel silver wire. For these guys, they play so much that they notice and are bothered by any change, no matter how small. These are the guy who we are pushing towards stainless frets, if we can get a size they like. So far, only a couple have taken us up on it, but those who have tried them have given us positive feedback, so I think stainless may well be here to stay. While the business man in me doesn't like the idea (fret dresses and refrets are high dollar labor jobs that make me a good deal of money), my right shoulder (and the right shoulder of all the guys who work in our shop) LOVES the idea of doing fewer fret dresses. It is REALLY hard work, and has caused at least a few luthiers to get tendonitis or carpal tunnel. This is somewhat offset, however, by the difficulty of doing the work on stainless frets.
Fret wire is a strange thing. I know amazing players who couldn't care less. But I also know amazing players who are fanatical about their frets. It goes both ways. I will say this, though. Fret wire is one of the only equipment things that I think players become MORE worried about the better they become. Most of the really great players who come into the shop will tell you it doesn't really matter what guitar or amp they play through. They have a sound in their head, and they will use whatever gear is at their disposal to get that sound. But where amateurs almost never worry about what kind of fret wire is on their guitars, and journeymen (for lack of a better term) will only occasionally get really anal about it, it is the great players who know exactly which wire they want, and who can't stand fret dresses. My guess is it is just that they spend more time playing, so they notice it more.
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