While i don't have the experience in salt water to comment, but i always thought the problem with salt was the start-up cost and water parameters.
Start-up isn't more then a planted tank, but the skimmer and lighting will cost more then the basics on a non-planted freshwater. The filters/powerheads can be more complex but are normal about the same.
With water parameters, you have such a small amount of salt water and it's hard to deal with the salinity, trace minerals, and general parameters, where you don't have to worry about much beyond the cycle and oxygen on a base freshwater.
As far as time, i'd imagine they are about the same. You gotta mix water for the salt, but beyond that it's the same water changes, cleaning and feeding.
I suppose FOWLR
is about the same as normal freshwater, with corals more like planted.
I dunno, if i had a 55g tank around i'd go saltwater, but smaller i think freshwater is much better.
Just my 2 cents.