There have been thousands of posts on other forums I visit regarding these devices.

I have a Drum Dial. I use it to get me into 'the ballpark' then fine tune by ear.

Regarding this and the Tension Watch, I can't really say which is better as I haven't used a Tension Watch. But I will say, if your considering getting one of them, that they are handy tools to have but not substitutes for learning how to tune drums.