The people I know use the EZ tatt.
We always used to use the clamp, and I think I am going to buy an EZ tat.
The thing I liked about the clamp style is its one quick movement and you're done.
We just tattooed a bunch of rabbits 2 weeks ago at a show. My does were uneffected by it. I don't think the girl was pushing hard enough to be honest.
and then we did one of her does, and she HATES the pen. So it was a pain in the ass because she would not sit still so she had to keep starting over. And wait for her to settle down. Honestly in this case I would PREFER the clamp.
and then I like the EZ tat better because someone who is good with it, makes the tattoo look amazing.