I think if it's the way back or the way out, it differs a bit. I also personally would like to take the ferry if I am returning home, after long holiday and long hour rides comparing to if I am just starting; then I would prefer to ride along.
I am leaving tomorrow From Helsinki to Hamburg with Stockholm ferry, that ferry was only 75 euros in Finnish web site (156 in English web site). I decided to take that route and ride through Sweden around 950 kilometers instead of direct to Travemunde and pay 500 euros, still some 100 kilometers to go.
Probably money-wise, it is not that different, didn't really calculate it, I want to cross the Oresund bridge :)