This topic is usually debated with a religious fervor here on UU, about every 4 months or so (at least in the 4 yrs since I've been here).
Coming from playing guitar my whole life prior to discovering ukulele, all guitars I ever encountered always had some form of GEARED tuners, and no matter how many times I've tried, with friction tuners, they are not for me.
From the cheap ones that are nearly useless and simply do not work at all against string tension, to even the spring-loaded, and/or high-end ones that fans of friction tuners rave about as 'the best ever', I find them extremely frustrating to use, to the point that if I buy a uke that has them, I will IMMEDIATELY replace them myself either with the Grover 9NB open gear tuners, which are about $15 per set everywhere, OR with the Gotoh UPT-L 'planetary geared tuners', which LOOK a lot like friction tuners, but have a gear system inside (think of how an old-timey clock works) and are seamless and awesome to use, but cost about $60 per set.
HMS sells and installs the Gotoh tuners, so if your uke is coming from HMS, you can have them installed, but it will add to the delay before it ships since additional work is being done to your uke, BEYOND their normal setup procedure. Adding a pickup will ALSO delay shipping to account for the time needed for the pickup installation.
- The problem with friction tuners vs other tuners, is that the only mechanical force that is resisting the pull of string tension, is some form of rubbing interference (friction) between different parts of the tuner, or the headstock wood itself, in order to prevent rotation of the tuner shaft.The advantage of friction tuners is that restringing is very quick because the friction tuners are a 1:1 ratio.
- With geared tuners (or machine heads as they are sometimes called), the tuner button is on a shaft that has a worm gear, and that worm gear turns another gear that is 90 degrees offset in rotation, and that second gear turns the shaft where you wind the strings on. The offset of the 2 gears creates a resting mechanical force that resists rotation from string tension. Unless the tuner is malfunctioning, this resistance is absolute, and when folks say that geared tuners 'do not stay in tune' this is an incorrect perception, because the geared tuners absolutely CANNOT turn by themselves from string tension, and ONLY by rotating the button with your hand.
This 'tuners do not stay in tune' which is littered all over Amazon reviews is simply pure ignorance over the fact that new strings for ukulele and classical guitar are made of polymer materials that take much more time to stretch and settle to concert pitch than steel string instruments (like electric/acoustic guitar, banjo, mandolin).
Geared tuners also have a ratio usually starting at about 12:1. which means that you must perform 12 complete rotations of the tuner button, in order to rotate the string-wound shaft 1 full rotation. Thus a manual or powered string winder is helpful, unless you literally enjoy, twiddling your thumbs while bringing the strings up to tension.
- The Gotoh and similar (but thinner) PegHeds 'planetary geared tuners' are based upon the same technology as the geared tuners used mainly for banjos. And have a similar system of gears, but all inside a barrel assembly next to the tuner button. They do have a 'reduction' or ratio, usually 4:1, and work similar in the way as a 10-speed bicycle, locked into a 4:1 ratio, which means 4 rotations of the tuner button - 1 rotation of the string-winding shaft, an these are much faster to restring, and more sensitive to altering the pitch when tuning than the previous tuners in #2 above. They are a pleasure to use, and well worth the upgrade if you have the budget, and also are usually lighter than any of the tuners mention in #2 above, this means that on a soprano or concert uke, you are less likely to have a headstock-heavy instrument.
Hopefully the above helps to understand the differences.
If not, ask away and either I or someone else will reply with more info.
[edited to add:] Funny - while I was typing out all the above, you guys Rolli, Mike and Dave, already beat me to it in explaining some of this, however, I will leave my post here any way. It's all good.