1. You will receive both special priority embarkation and debarkation in New York City. Just follow the appropriate signage to the VIP check-in area. From what I understand, this really does make a difference during peak times.
1a. As far as port of calls perks, for suites I do not know of anything special unless you are of platinum status which you are not since you only sailed Carnival once.
2. I have never heard of Carnival having concierge service on its ships, but then again I would also say that the suites are not nearly as big/nice as other cruise lines.
3. This one is personal preference, rooms tend to be bigger in the aft, with a nice large rap-around balcony. However if you are more prone to motion sickness, you may choose a standard suite in the center of the ship as you will feel the motion less in the center than in the aft.
4.Special features include a large vanity/dressing table, refrigerator and entertainment area, VCR, whirlpool bath and walk-in closet.
Miracle was a very nice ship, a little too overly decorated in my opinion, but it did just come out of dry dock and apparently as been renovated and some of the unnecessary decorations have been ripped out. In my opinion I enjoyed the Legend much more than Miracle due to the difference in entertainment staff onboard, but these things are all subjective and are likely to change in any given week. I feel that you can't go wrong with any cruise on a Spirit Class ship!