This old Chestnut?
I would think/experienced any exposed bare copper wires (crimped wire ends, etc. being connector'ized ) in a boat (esp salt) are better off covered up/protected from the elements. So if by design (there are others, yes), one happens to be using leaded tin (soldering) as a covering over the copper, actuality this then helps prevent corrosion, doesn't it?
This is of course is as far as corrosion factor goes on the exposed copper wire BUT, if the copper wire being used comes pre-tined (i.e. "marine grade wire") then proper crimps are fine as well. Is the coax "marine grade wire"?
If I recall right, the center conductor is usually just un-tinned copper.......And how exposed is the inner copper after assembled? I've seen them rot inside over time and elements.......
I think they also offer tinned inner mating conductors in that connector due to being inherently more corrosion resistant.
Anyway.........Other consideration come into play when soldering: wicking, flexing, vibration, strain relief, yada yada yada. Here's what the "experts" say about it.............In a nut shell and my interpretation is: A sole solder connection is okay AS LONG AS it has strain relief. See "If soldered" below
ABYC
11.14.5.7 Solder shall not be the sole means of mechanical connection in any circuit. If soldered, the connection shall be so located or supported as to minimize flexing of the conductor where the solder changes the flexible conductor into a solid conductor.
EXCEPTION: Battery lugs with a solder contact length of not less than 1.5 times the diameter of the conductor.
I believe if I recall correctly, the PL-259 connectors have built in strain relief in the back shell.