You can't compare iMovie to Premiere Elements any more than you can compare Premiere Elements to Final Cut. Or a Hyundai to a Greyhound bus. They are very different programs working in very different environments for different purposes.
Your biggest issue is that you're editing video that's been created by Handbrake, which is an iffy proposition no matter how you look at it.
Premiere Elements is designed to interface with video from miniDV, HDV, AVCHD and Flip camcorder as well as video from higher-end DSLRs like the Canon D series. Non-traditional sources, including many pocket cams, can cripple the program.
Before you buy any program, I'd test drive it and see if it works with your source video. That should be your priority. Because if you can't get it to work with your video, everything else the program does is moot.
I cannot speak for iMovie, or FCE, but one of the beauties of Premiere (either Elements, or Pro) vs FCPro, is that the Adobe programs edit most common formats/CODEC's natively, where FCPro internally converts all footage to proxy files (usually a flavor of ProRes), for editing. This is often not that smooth a function. Depending on your system, the exact Source Footage, and a few other factors, editing in either flavor of Premiere should be smoother, and quicker.
As of the release of FCPro X, many users are jumpting ship for PrPro CS 5.5, and after the initial "shake down" with it, are loving it.
I agree with Steve - a test-drive is the best way to determine whether a particular software is right for you.
Good luck and happy testing,
From my small experience of softwares (Windows movie maker, Sony Vegas, iMovie and
PRE) , I decided to use Premiere Elements on my Mac and my Vista laptop.
Reasons : Movie maker and iMovie are simple to use, for input capture : most types of cameras
(DV HDV or AVCHD) are recognized.
If you want to edit movies only by doing cuts in rushes, and assemble with simple titles, they
Programs like PRE or Final Cut allow you to have multiple tracks of video/audio, and you can
combine more easily your clips. It's a different way of editing which needs learning, thanks
to books (Muvipix in the US, little choice in my country France...).
For Premiere, Bill and Steve give us a lot of important things in this forum. Thanks to them.