Sailed on the Explorer 2 in May this year, and despite this being an older ship we preferred it in all respects except for the cabin.
The weather was fantastic all week, and we opted to do our own excursions courtesy of research on cruise critic reviews.
We travelled as a couple in an iinside cabin on deck 3.
Inside Cabin on deck 3 allocated upon arrival, below the main dinning area and no noise disturbance at any point of the cruise.
Room was clean and tidy with all amenities you required, but a bit dated.
Only issues to us were that the beds on Marella are very firm, which may suit others but just not us, and bathroom shower is too small to have a shower screen so uses a curtain which is never ideal.