I've used both. I tend to have a full-ish grey water tank when dumping the black so the slinky isn't that bad. If I can use my screw on fitting at the dump station or campsite, leaks or dribbles are minimal. Plus, the volume being emptied by a full slinky is a lot more than a macerator pump can grind through.
The macerator pump does one thing the slinky can't, and that is pump up a height to a dump tank in my truck or a rented 250 gallon tank that the honey wagon empties.
For a "B", I'd go for a macerator pump installed because there isn't much room to take the portable one, and there are times where one might use a hose to empty in a toilet or clean-out.