I'll not be of much helping you choose the right software, I don't live in the propietary/privative software, I prefer the open source/free/libre world, so, my software environment is the following:
Operating System: GNU/Linux, Fedora 16
Video converter: ffmpeg
Video Editor: Kdenlive
Panasonic Lumix ZS3, Video Format: 1280x720, 720p 30 FPS, MTS container, AVCHD/AAC Lite codec
GoPro Hero 2, Video Format: 1080p 30FPS, 960p 60FPS, 720p 60FPS, MP4 container, H.264/AAC codec
I've also tried some other cameras (Lumix FZ150, SONY HX10, JVC Everio, SANYO Xacti, etc.), in almost all cases, I download the video files from the camera's SD card, convert from the camera format to MOV keeping only the "intra" frames:
ffmpeg -i CAMERA.MP4 -sameq -intra IMPORT.MOV
then I use this file as the input to the kdenlive editor, this in turn builds a "proxy" that is low quality version of the input file used only during the visual editing process to reduce the hardware resources needed to edit large format (HD) files. Once I decided the clips I will keep, put them on the timeline, generated all the transitions and effects and added the sound track, I use kdenlive to render the output into a very large uncompressed AVI container in the same resolution and FPS as the input file (it is very important to avoid converting to higher resolutions or changing aspect ratio).
Finally I use ffmpeg again to convert from this huge uncompressed file to a format suitable for the final use of the video, for example, to upload it to YouTube, I generally convert to MP4(H.264/AAC) in 1280x720 (HD720) resolution with a 3Mbps bitrate. For VF, where we have to stay under the 20MB file size limit, I generally use the same video format as for YouTube experimenting a little with the bitrate until I get to a file just under 20MB, that is the highest quality possible without surpassing the 20MB barrier.
I know most Windows users don't feel comfortable using command-line tools, but I understand that the ffmpeg audio/video converter is available for Windows too. There is also a graphical tool based on ffmpeg for Windows called SUPER, I tried it once and it seems very simple to use and loaded with lots of options and doesn't require a separate codec pack.
I'd suggest to experiment with your preferred video editor until you find the right input file format, then simple use ffmpeg or whatever video converter you use to convert from the camera format to this "import" format, try not to ruin your video during the editing/rendering process and then convert again to the final format/s
In the end, it is important to understand the some of the details behind the editing process, file/container formats, codecs, etc and take the time to learn the tools at your disposal. I've seen many people using very expensive hardware (computer/camera) and even more expensive software only to produce sub-optimal results.
Hope this info useful to some other pilot.
Regards from Buenos Aires!