No, I don't.
Clarity is 12.9% Representative APR (What did you get?)
Zero is 18.9% Represenative APR
This means that if took out £1000 in cash and didn't pay it back for a whole year, you'd be charged approx:
Clarity: £129 (35p a day or so)
Zero: £190 (50p a day or so)
Now of course the fact you've got one of these cards means you are being smart, and given you are being smart you wouldn't leave a balance on it for a year anyway.
If you left it about a month - ie, you just left it to get paid off by a direct debit, in full:
Clarity: £10.50 interest (Remember, this is on a £1000 withdrawl, so its basically 1%!)
Zero: £15 interest (So basically 1.5%)
The sooner you pay it off the less interest you pay. If you've got online banking its pretty easy to transfer money over to the card after you've made a cash withdrawl.
But then its unlikely you'd withdraw a grand in cash anyway, so in reality the cost difference between them is even smaller.