How do you intend to use the light?
The Quark should be noticeably brighter and has more modes....
Just noticed that Selfbuilt has the P20A2 in his review here and it's not as powerful as the P10A2 for throw values:Forgot about these so if you wanna vote for them just copy and paste a comment.
* EagleTac P20A2 'cool white'
* EagleTac P20A2 'neutral white'