As a novice, I have read that PL259 is not recommended because it isn’t sealed as well as N, but only because it isn’t as weather resistant as N.
The "UHF" series of connectors, including the PL-259 and SO-239, were essentially designed as a shielded banana plug.
"UHF" back then was a bit more loosely defined as anything above 30MHz. Now, UHF is considered 300-3000MHz.
The UHF connector is fine for VHF and will perform 'well enough' at 460MHz. It's perfectly usable for amateur radio/hobby use. You won't see them quite as often in the professional field. A lot of VHF mobiles will have UHF connectors. Some UHF mobile radios will have them, but usually lower tier radios.
At higher frequencies, like where your discone works, UHF connectors start to get problematic since they do not provide a consistent 50Ω impedance.
Again, not a big deal for hobby use, a bigger issue for LMR/higher power stuff where there's a lot tighter requirements and challenges that come into play.
UHF connectors were never designed to be water resistant or water proof. They were never intended to be used at these higher frequencies.
N, BNC, TNC, SMA, all better choices for this sort of stuff. Not saying you should replace your antenna or coax, it's fine for what you are doing. But, if you do ever replace your discone, spring for the N connector versions.
N connectors do have sealing that makes them water resistant, but no professional radio guy would ever install one outdoors without proper sealing of the connection.
As for connector sealing, this is the generally accepted professional method that has been proven to work well:
