Wearing just life jackets, unless they are gliding in from FL200 in a motor glider (and thus give the rescue services a good head start), or they ditch close to some boat, they will likely be dead by the time the official helicopter reaches the scene.
So buy an immersion suit. Cheaper and far lighter than a liferaft, and will keep you alive until the emergency services reach you. I bought one after attending a ditching course and finding that I couldn't get into a liferaft...and that was in a swimming pool!!! It's reasonably comfortable; I wore it when flying from Oban to Barra on a very hot day, and it was OK.
Why are these lifesavers so rarely mentioned?