Neither, I have tried them, but for me the overlaid fast scroll bar in Perfect Browser, so I can scroll up and down a whole long web page by moving my finger around 3" on the iPad screen is the biggest plus of any 3rd party web browser.
I would recommend spending the $3 (I believe) and using iCab. From what I've read around here they are very much alike, but most prefer the UI of iCab.
For those that have purchased iCab, does it allow you to DL on both iPad and iPhone without paying twice?
I have not tried iCab, but I use Atomic as my only browser on my iPad 2. I like the adblocking and Dropbox integration. Tab support works well and the finger gestures to get to the top/bottom of a page quickly are very handy. It also goes full screen with a simple three finger tap. The only issue I found is Etrade, none of the links work after logging into your acct.
I did a YouTube video a couple of weeks ago with the latest Atomic 5.5