The Shubb c7b Capo first appeared in 1996, and was the first partial capo to appear after a 20-year stretch when the Third Hand was all there was. They are only made of brass (which is what the letter "b" is for in the name) and they currently come in only one size, and without the so-called "deluxe" roller mechanism that the most expensive Shubb capos (The "S" series) use. There is a brass screw on the back that you adjust for the thickness of your neck, and once you have that adjusted, you just snap the capo on and off.
The Shubb capos are low-profile partial capos, which means they do not get in the way of your left hand and they are easiest to reach over and behind. They are barely visible to the audience. And they fit easily in either a shirt or pants pocket.
Shubbs are extremely durable. I have Shubb capos 20 years old that still work fine.
You can get the tension just right. Because of the adjustment screw, as you move the capo from guitar to guitar and up and down the neck of a single guitar, it may not fit the same. With the tension just right it will sound good and not pull you out of tune.
The Shubb c7b capo has a longer "foot" than the Kyser. The only disadvantage of this is if you use it with a super-narrow guitar like a Fender electric, you may need to file it down a little. With a wider neck guitar, or even when you go up the neck, you may find that the Kyser capo "foot" (only 7/8") is too short to cover all 3 strings, since string spacings tend to increase as you go up the neck. The c7b (1") will usually work at fret 2 of a classical or a 12-string, which the Kyser will not.
The Shubb capos are easy to saw off and file down. The soft brass cuts like butter with any hacksaw (even a Swiss Army knife) and once you get into partial capos, you may find yourself wanting to modify your capos to fit certain guitars and to make single-purpose partial capos that clamp fewer strings, for example.
Shubb partial capos come with no instructions. My new "Capo Voodoo" books have thousands of chords and dozens of ingenious ways to use one of these capos. Thousands of players have been unable to find them in over 20 years, and you likely won't either. The capo comes with essentially no information. This is not a small thing. It is not obvious where to put a partial capo to get music.
You might have to adjust the screw. Many guitar necks get thicker as you move up the neck, so a drawback to this capo is that when you place it at fret 5 or higher it usually requires a little fussing. On stage this can take precious time between songs if you need to do something like move it from fret 2 to to fret 7.
You might have to buy a brass full capo to match one. Many of us use partial capos together with full capos, and if you have a silver (or black is the other color Shubb makes) full capo it won't look as nice.
The rubber sleeves are little too soft for my tastes, and dull the sound slightly. After a few years, the rubber also gets soft and oily and needs to be replaced-- which costs less than a dollar. However, the softer rubber on the Shubb does a good job of clamping the octave string on a pair of 12-strings.
There is only one size The c7b fits most guitars, but won't work above the 2nd fret on wider necks like classicals or 12-strings. (Luckily you can saw off a c8b to do this.) You will need to snip off the rubber sleeve with scissors and maybe file down the capo's brass foot a tiny bit for a super-narrow neck like a Fender electric. Or if you use a narrow electric as well as an acoustic, you might want to buy one Shubb and one Kyser.
Kyser partial capos appeared around 1999, and have become favorites among certain groups of guitarists, especially the singer-songwriter crowd. They are spring-clamp operated, and are made of enamel-painted aluminum.
The Kyser capos are the fastest-action partial capos. They can be popped on and off the guitar almost instantly, and moved up or down the neck even in mid-song.
The rubber foot of the capo makes a very nice tone. It's a little harder than the Shubb, and sounds perfect to my ears. It may not be able to clamp the octave string of an octave pair on a 12-string or octave mandolin, though.
Kyser capos don't need to be adjusted. No screws to turn- just squeeze the clamp and put it on the guitar.
Kysers are easy to store on the headstock or strap. No more fumbling in your pockets or keeping a table next to you on stage. Many players store several Kyser capos on the headstock or strap.
Kysers fit narrow fingerboards like Fender electrics. The Shubb is too big (1") and needs to be trimmed down a little.
Kyser capos come in a lot of cool colors. Fashion is important, and it is also easier to keep track of which capo is which ifthey are different colors. If you play in a band or with your spouse- get different color capos and it instantly solves the problem of "wandering capos"!
Kyser Short Cut capos come with virtually no instructions. It is not obvious where to put a partial capo to get music. The Kyser Shortcut capo comes with 4 chord ideas and almost no information.
Spring capos are just weaker than clamps. They grow weaker with time, and even new ones may not have the strength to handle 12-strings with pretty heavy strings.
The Kyser Short-Cut capo has a shorter "foot." The advantage of this is if you use it with a super-narrow guitar like a Fender electric. With a wider-neck guitar, and when you go up the neck, you may find that the capo "foot" is too short to cover all 3 strings, since string spacings tend to increase as you go up the neck. The Kyser will not work even at fret 2 on a classical guitar.
The spring mechanism is very visible and obtrusive. Your audience will see this capo, you will bump into it when you play over and behind it, and it will not easily fit in your pocket. It is just not as "sleek" as the Shubb.
There is no way to adjust the tension. You just hope the spring is strong enough, but not so strong as to pull you out of tune. On a fat neck guitar, or higher up the neck on any guitar, you may have trouble with too much force.
This is not entirely true, and the Kyser capo can be "adjusted" somewhat by bending it. Here is what Greg O'Haver says is the way to do it: "Looking at where the upper rubber that contacts the strings touches the lower rubber that rests on the back of the neck. When you first get your Kyser capo these two rubbers are touching each other. Opening a gap between the two will lessen the pressure and eliminate pulling your guitar out of tune. By placing your thumb over the point where the lower lever pivots and using your other fingers to bend the part with the lower rubber, we can open that gap to about 1/4 of an inch or so. When you get it to the point where you put the capo on your guitar and it doesn't pull anything out of tune but holds down your strings without buzz, it is adjusted for life. It will reach a point where it doesn’t want to bend anymore and that will be enough adjustment. It doesn't take much adjustment to achieve this so adjust it in small encrements."
The spring capos can pull side-ways. Spring capos do not distribute the force evenly, and high up the neck or on a fat-neck guitar, you may be unable to keep the Kyser in place (it often will pull sideways) and you may be unable to keep it from pulling the strings sideways out of position on the fingerboard.
There is only one size and they are hard to modify. Like the Shubb, they come in one size, and the hard aluminum and the fact that the rubber foot is glued on means you may need a power saw to trim one down.You will have a hard time with a wide neck or 12-string, and to use a Kyser you will need to cut down a "Drop D" capo and hope for the best.