Yeah it's supposed to be a little smoother in the treble, like the GR07 BE. I haven't heard it, though.
Of all the universal IEMs I've tried the UE600 is tied with Phonak's models for the most comfortable. I have small ears so what works for me might not work for others, but they're very easy to put in place and unlike many others require much less fiddling to stay there. Also, kudos to the design ethic making the right side red and the left black, there's no eye strained searching for tiny L and R markers.
Joker nailed the sonic characteristics dead on.
I agree, the fit of the UE600 is very easy-going. It does remind me of the Phonaks as well
You might want to double-check in the long MH1C thread but I think the MH1 uses an alternate pinout and only works if you have one of the older Nokia or Sony smartphones. It will need an adapter to work with newer ones. Not sure how it interacts with a simple stereo jack (one without headset functionality).
Unless you want the more forward mids and/or the adjustable-nozzle housings of the GR06 I would go for the VSD1.