I've heard good things about the Paige 12 string Capo, and I currently have a Kyser.
I am partial to Schubb capos. They grip well, they are durable, and they are unobtrusive.
For a 12 string *anything* is better than a Kyser. The Paige is pretty good but I find them a little awkward to set. I really like how it stores behind the nut. For the way my guitar sounds for some reason my Planet Waves NS sounds noticeably better on my 12 string than anything else in my capo collection. I couldn't begin to speculate why. It also costs about half of what a Paige does.
I just got a new Kyser as my old one for the 12 got too loose (fine for 6) - I find the Schubb's are better but you can't easily clip them to your head stock. While I was shopping for it I ran across some Schubb 'Cut Capo's' for about 29$ - I bought one on a lark and this thing is incredibly fun - especially for 12 string.
When you capo up 2 (Strings 5,4,3) it puts the guitar in a E sus chord - the same voicing as DADGAD. I have a bunch of DADGAD songs but de-tuning mid rehearsal or mid gig can be a nightmare. When you flip the cup capo around, second Fret, stings 4, 3, 2 - it turns into Open A.
It's funny but both these tunings still work in D, C, G, chord structures - if you stick to 'Farmers Corner' it's almost impossible to hit a bad chord. In the E Sus mode you can even do an F#m with your index finger below the capo on the open E string.
Waking up this discussion :)
Best 12 string capo for Seagull/Norman 1.9" nuts (exclude Paige and Bill Russel Elastic from replies please)
I seem recall both Kyser and Shubb mentioned generally as having great 12 string models but do not recall nut width mentioned.
With 12 string nut widths ranging from 1.69 to 2.1, I'm sure some 12 string capos would struggle at those extremes.
Jack i have a Planet Waves NS in my collection and I agree it is best of the bunch, certainly better than the Bill Russel 12 and the Paige Clic 12... but it IS a 6 string capo and the wormscrew design is slow to manage.
The Planet Waves Ratchet might be ok if there was a model that could actually fit around a 12 string neck.