Prefer one hand with the Kobo Forma and Oasis 2. The Forma is incredibly comfortable due to the angled strip with the buttons, the larger size, and soft material. Doesn't even need a case.

On the Oasis, not as good. I have larger hands and find I cannot get a comfortable grip. It's slippery due to the aluminum, and also I cannot find a comfortable position where I can both hang on it to adequately, AND position my thumb for extended reading. I have a 'grippy' type of case on the way from Amazon that I'm hoping will solve that problem.