Been on 2 MSC cruises and found the dress code to vary, most were in short cocktail dresses, maybe 25% in long gowns, but was shocked to find some didnt even bother to dress up. enjoyed cruise though.
Europeans tend to be casual dressers by day and even in the evenings some of them don't go to much trouble outside of the captain's formal welcome and farewell gala evenings. It's worth taking some smart outfits along for these but otherwise you can dress pretty much as elegantly or casually (within reason) as you wish without exciting comment. I'd take the LBD.
Ya it looks good .I have got many chance to wear Short Cocktail Dresses on such occasion . Long Gown can be possible but very less.