Thank you DNSB. You have cleared up my confusion nicely. I copied and pasted the dimensions directly from the Kobo.co.nz site and I assumed that all dimensions were listed in the same order for each device. That would have seemed the logical thing to do. They listed the depth last in each case, why invert the length and width?

But now that I know they inverted the listing order, the H2O looks more appealing, as it was the 172mm "wide" that was my biggest concern. Now that I now it's only 129mm wide, I am more inclined to give it a try. Many thanks!