I was between the MS1i and the AD700 awhile back, and I went with the AD700s - I don't have any experience with the MS1i but I love the AD700s.
Their sound stage is as wide as anything I've ever heard.
If you're also a fan of treble, you're gonna love these. Every time a cymbal is hit, I can hear it shimmering into silence.
The mids are very neutral - guitars are precise, and not too "in your face." Male vocals also sound really nice and natural.
As far as bass goes, it is tight. And by tight, I mean tight. It is definitely there, it just doesn't have any boom. Bass drums have a good thump to them, and bass guitars sound very smooth. If you are into bass at all though, these aren't the cans for you. They don't lack bass, but it's extremely controlled.
Overall, their sound is very relaxed and nonfatiguing - I have listened to these cans for albums on end with no problems. I love them.
For the mere price tag of $90 I would definitely say go for it, unless you want the "in your face" sound of the MS1s.