Unless you want a smaller device which would be a little more portable, I'd go with the 505. £10 cheaper, and it'll come with a cover--the 300 only comes with a sleeve, so you'll have to spend even more money if you want a cover. And as Superlucky the devices are basically identical, except for the size and the 300 not having any card slots. I do think that the 300 does have more internal memory than the 505 though.
dordale