This is really just personal preference. When it comes to mice and pointing devices, perhaps even more so than when it comes to keyboards, your specific anatomy, habits, setup and preferences decides what would work for you.
Personally, I use two pointing devices. One is my work thumb trackball (I have one at home and at work). I am a big fan of the thumb trackball. It creates zero strain for me, I am quick and accurate with them, and they are in some ways better than a regular mouse (especially if you use multiple screens and are constantly moving the cursor between them). I have used and tried the "large" trackballs like the kensington slimblade, but they are not for me. They are slower to use and less comfortable for me, even when I gave myself enough time to get used to them.
But there are certain applications in which I prefer to use a regular mouse. Gaming is on example (but not the only one). For that I use the Zowie EC1 Evo (white). One reason to use this mouse is the optical sensor that outperforms a lot of popular sensors on the market. But the main reason is low weight for its size, the perfect (to me) shape, and the glossy coating that just sticks to my hand and feels pleasant.
Those are my choices. I do recommend them but at the same time, I do realize that for someone else, a glossy coating , or a trackball that you operate with your thumb, could be a nightmare to work with.
