Steadicam Merlin or Glidecam HD-4000?

I'm curious to know people's opinion on these two products. I have seen a few demonstrations on these products via youtube videos and they both look like they work great.

I just need a couple of feedbacks, opinions, or reasons why one is better than the other.

Please leave a descriptive response, not just a yes on this and a no on that. Thank you, your help is much appreciated!

P.S. --- Oh, and just to give you guys a little background, I own a Nikon D7000 at the moment and plan to upgrade to a Canon 5D MK II in about 6 months.

Added (1). And another thing, I was wondering if it is possible to mess with the aperture or zoom while filming on these two.

I'll only comment on one statement you made. You can't "film" with this camera because it doesn't do film - it does video. This term is so abused and it's absolutely wrong when it comes to digital cameras.

I don't know who you associate with but if they're pros you're going to embarrass your self if you don't know your terms.