Neither. A microphone mounted ON THE CAMERA is pretty much the WORST POSSIBLE place.
Since you didn't tell us what you are doing, what kind of stuff you are shooting, it would be silly for us to try to recommend anything.
No, there are TWO issues here.
One issue is what you are recording ON. You say "trying to avoid dual sound" which we assume means that you want to record audio on your DSLR.
But the SECOND issue is WHERE you PUT the microphone. Physically attaching the microphone to the camera is a TERRIBLE place and is NEVER recommended.
If you are trying to shoot scripted drama on location in the Real World for example, a microphone on the camera will NEVER EVER give you decent dialog recording.
There is no situation you can name where a microphone (of ANY kind) mounted ON the camera will give you good results.
A possible exception would be a documentary about adams-apples or neclaces with lots of close-ups of people's necks (so that the microphone is aimed at their mouth).
I have had pretty good experience with the RODE Videomic pro on my GH3. I'd highly recommend getting the dead cat for it so you can use it in wind. I don't think the Sennheiser is really any better. Obviously, they both perform like short-shotguns attached to your camera, so you mileage will vary but I'm going to assume you know the limitations of mounting your mic to your camera.
well, based on my tests, am going to simply use the on board stereo mics on my Zoom H4N direct to camera.
This is background, not my primary audio and to my ears, the quality of the audio from the Zoom mics is MUCH better than the RODE.
Of course a little less directional but vocals sound simply fuller and less harsh-thin to my ears.
I purchased the RODE based on all the good reviews, but I think you need to do your own tests and make up your own mind. I would definitely use the RODE but only if the only other alternative was in camera mic.