Antarctica is a very special place. We very much wanted to go, but as someone who does not cruise we were a little ?? about having to take a cruise to do it.
Note: there are other options, but they are extraordinarily expensive, one lives in tents and there is no wildlife to speak of.
Anyway, I cannot give any kind of comparisons to other ships, so I will just give you our view from that perspective.
Get a room mid-ship - helps in wild seas. Bow is not good. We likes 427(or 422) deck 4 mid-ship right over the stabilizers. The windows are too small on deck 3.
If you have the cash - go for the silver suites mid-ship(527/522). I would not spend the money for the Medallion, Grand or Owners Suites, unless sea sickness cannot happen -- they move a lot.
427 - large room, great closet, big bed - we loved it.