The clear tamas always feel interesting, even though there is no difference ....
but why not get all four? The seller does combined shipping.
I'm still watching the pink Keitai, but I do not like the orange tama that comes with it. (I am really picky about the casing design.) I could always resell the orange one, but I am afraid that nobody will bid on it. I couldn't sell my extra uratama on eBay (it was only $11!), so I guess people are not that interested in buying Japanese tamas.
But anyways, keep us updated on which ones you actually get.