I've made a study of this and I think the best I've had is the Goodmama one. Followed quickly by WN (although we never had OS - only side or front snaps). I had an old Happy Heiney and it was dreadful.
I think you'd have a job getting hold of an Itti Bitti one anyway, I couldn't get a cow print one anywhere! (or maybe I just didn't look hard enough, lol). I bought a limited edition 'strawberry fields' (the red polka dot one) Itti Bitti from cheeksandcherries.co.uk, they said I'd got the last one in that colour and that the cow print had been sold out for ages and that most places are having trouble getting any more in