I think every overwater trip deserves it's own appraisal on what survival gear to take bearing in mind comfort and practicality against risk. Main factors to consider are type of A/C, POB, distance of crossing, time off year, sea state / weather conditions (vis etc) on DOF.
Personally in the arrow, I would just take a raft and PLB on channel crossings etc up to 75nm overwater in the summer on a fine day with pob's. But the same crossing in the winter or in bad weather where we may not be found for much longer survival suits would be a good idea. If I was crossing the North Sea by myself direct from Newcastle to Texel in the winter/spring I would definately have a raft, survival suit and PLB/ELT as a minimum.