I don't own either of them, but they've only been reduced to £10; they were originally £40, which is more within the good quality rechargeable vibrator price range. :)
I own the serenity one, only got it the other day so havent used it enough yet to give a proper review. It is definatly a bargain at £10, very powerfull and gets results. I think the only issue with it, is the noise as it is very loud but if that doesnt bother you then I would say buy it as personally I think for that price you cannot go wrong.
they caught my eye when i saw they'd been reduced to £10 maybe it's just how they look in the picture but they kinda look pound shop cheap while i don't own those particular vibrators i do own a few california exotic toys and they don't scrimp on power for a tenner they are woth a punt if you don't like it you can send it back