Here's an interesting and totally biased perspective being a salt water boater... Since I run in salt water I "have" to flush my engines everytime I go out even if it's for 5 minutes and a soap/water wash down is a necessity as water alone does not get rid of salt... So in general I "have" to care for my boat where as a fresh water guy might get lazy about it because he/she doesn't "have" to.
At the end of the day, when buying boats I don't consider fresh/salt as my purchasing factor, just over all condition.
Don't believe all the hype about the "salt water monster" but yes, it does require some extra care and I actually enjoy it! When I get back from a nice ocean run I'll grab a beer and start cleaning up... Sometimes I even tell my wife to go home or go lay down in the cabin so I can spend extra time cleaning and not be rushed etc.... It's like therapy and gives time to reflect on the great day we just had, kinda like yesterday!