Head Turner,
Apart from your own early mention of the 900, there's been no talk of the MD offering. It's perfectly capable of the USL ops you describe - our company intranet has some good pics of the recent JATE trials with all configurations up to 80 ft strop. Your own observations about the superb cabin hold true for pax comfort and visibility. Build quality is not so robust as the Eurocopter models, and as has been said in previous threads the NOTAR takes away payload equivalent to one pax.
Based solely on my limited experience (902, current 135 and a few cabbies in early 109s - the 212/412 probably doesn't count as they're a bit larger), I'd prefer the 902 over the rest so long as yaw control and long range weren't an issue. The 135 is well built, loads of yaw authority but a tiny cabin and - to use a phrase beloved of an instructor I know - the pilot was definitely not in the office that week when they put the cockpit together. The learning curve on the CPDS and AP is steep; it's nowhere near as intuitive as the 902. Why they need separate FADEC switches only Eurocopter can say, and for a lesson on twist-grip throttles take a look at how MD and Bell do them. Haven't operated the 214ST, but those throttles look fascinating...
If 7 pax IFR is what people are looking for, I assume the 145 would be under consideration too.