The 5227169-4: The nickel-plated zinc body gives it a standard silver appearance suited for indoor RF test equipment, instrumentation, and telecom infrastructure where the bayonet lock provides quick connect-disconnect.
Termination is solder cup on the centre contact, which means you tin the centre conductor of your coax cable, insert it into the cup, and solder. This is a field-terminatable design but requires a soldering iron — no crimp tool needed.
The 500-cycle rating on the 5227169-4 is a solid durability figure for a bayonet-lock BNC. In a test lab where a cable gets swapped daily, 500 cycles translates to roughly 1-2 years of regular use before the contact wear might start to degrade signal integrity. For a permanent installation that gets mated once, the cycle life is irrelevant — the gold plating still protects against oxidation over the equipment lifetime.