Thanks for all the very helpful comments! I wasn't keen on the Aura when I saw it as I didn't think the text looked as crisp as the Glo HD.
The waterproofing of the H2O could be useful - I have a toddler who likes to chuck water about
. Not bothered either way about the memory card slot - thought I'd miss one when I came to the glo after a Sony but haven't missed it at all.
Good suggestion about looking in whsmith - I would like to see how much larger/heavier the H2O is. I think dimension wise it's about the same as my old Sony case with a light, so I think that would be fine, but would be good to see whether I'd like a larger screen or not.