To be honest, far as I'm concerned both of these seem to do the exact same job. My skin doesn't feel anymore or less cleansed and soft with either or. So they both do they same job, to the same level.
What about Price?
For 100ml of Liz Earle with two muslin cloths will set you back £14.25, whereas Superdrug will give you 200ml of product with one muslin cloth for the price of £5.99
Is the muslin cloth any good?
I have to say you can instantly feel the quality of the muslin cloths provided with Liz Earle whereas the Superdrug ones don't feel cheap but they don't feel as good. But if Caroline Hirons says you don't need a muslin cloth if you own a flannel then what does it matter?
EDIT: I've just checked the ingredients for each product and they're quite similar except for their extracts. Liz Earle has hops, chamomile, rosemary, eucalyptus and cocoa butter and Superdrug has cocoa butter, vitamin e, a, f, b5 and h and horse chesnut.
Overall I'd opt for the Superdrug version, it does the exact same but costs less than half the price, for twice as much product. And you can always buy muslin cloths from Liz if you really wanted to.