Kevin Reylek has put together an interesting review article with B&H Photovideo that reviews the leading external microphones available for the Canon 5D MkII.  The review focuses on the Rode VideoMic, the Rode Stereo VideoMic and the Sennheiser MKE 400 and includes a set of audio files that allow you to compare the outputs of each of the devices with their various filter options.

The conclusion of the article is that the $199 Sennheiser MKE 400 is the clear winner in terms of compact size and weight, while the Rode Stereo VideoMic at $249 offers great customization options and is the most practical stereo option tested (albeit it was the only stereo mic tested!)

Back in December, Vincent Laforet had less kind things to say about the Sennheiser products and recommended the Rode Stereo Video Mic as a good solution - as long as you don’t want to look through the viewfinder when it is mounted on the hotshoe.

As you might expect there has been a reasonable amount of discussion on Cinema5D about microphones, including some hissing and gain issues with the Sennheiser which raises a few concerns.

Taking all of these views into account as well as looking at the sample videos posted below, right now, if you want a self powered mic to use onboard the 5D MkII then EOScars would lay the cash down for one of the Rode mics. The main type of shooting you are planning will dictate whether you want to go for the stereo or mono.

Comparison of Canon 5D MkII built-in mic with the Sennheiser MKE-400 and the Rode NTG-2 shotgun microphone:

Comparison of Rode Stereo and Mono VideoMics:

Rode Stereo VideoMic Test 1:

Rode Stereo VideoMic Test 2: