I pretty much abandoned Kindle in favour of Kobo about four years ago. IMO, the Kindle UI had become so awful as to be not far from unusable. Like you, I find the smaller devices more comfortable to use, and for much the same reasons. My primary e-reader is also a Clara BW.
You commented on the customisability of the Kobo. In case you aren't already aware, further customisations, beyond those offered as part of the standard firmware, are possible. You might like to investigate them once you've got fully used to the standard offering.
1.
Kobopatch allows you to tweak the UI to suit your own tastes. For example,
- "Remove footer (row3) on new home screen" will remove the advertising that normally appears just above the icons at the bottom of the home screen;
- "Don't uppercase header/footer text" changes the book title at the bottom of the reading screen from all upper case to mixed;
- ...and so on.
2.
NickelMenu adds custom menu items to various menus in Kobo's eReader software.
3. Setting your device to Sideoaded Mode might be a bit extreme for you, but I've found that I like it. It disables Wi-Fi downloading direct from Kobo entirely (both books and firmware), and requires you to load books manually, using something like Calibre (which I favour) or Adobe Digital Editions. It also disables the home screen altogether.
If you haven't already read
the thread about Amazon having removed the dowload and transfer option from its web site, you might like to do so. They've made it more difficult to transfer your Kindle books to your Kobo, but it can still be done (for the moment...).