It took some time to get used to it. The bigger size is not as comfortable to hold as the little one. After a while I took the MP3player, which I wouldn't have thought. I read along while I listen to unabridged readings (audio books). A very interesting way to make difficult texts easier to grasp or to enhance my inner voice with some new tonalities.
It also helps that 650 is dressed in an Oberon cover and now feels heavenly rakish
All in all if I ever were to decide between them I'd go for the little one anytime.