I'd go for megazorb, I've seen carefresh and the 'clumps' are really big, whereas with megazorb the pieces are fine and soft.
My robo seems to love digging it all up
Also it's considerably cheaper, £7-£11 for 85l
The only problem (if it could be called that) is storing things like the megazorb. Already got to find a place to stuff a finacard bale, and my backroom is a mix of sports'n'hobbies, and pet equipment! Got an week trial for a new job, which would involve moving - one thing I'm looking for in a new property is extra space to keep things like bales of bedding! It is that, or fit it under the coffee table