N connectors are for 220 MHz and above. Below that, forget it. PL-259's are the way to go for anything under 220 MHz. And they will handle a lot more power than N's will even with higher SWR.
You have to be really careful assembling some N plugs, constantly watching the distance between the center pin and the end of the connector. It's critical. If they stick out too far, they'll jam against the female socket and damage it. If they don't protrude far enough, they won't contact the socket pin enough (if at all!). This is a direct function of the coax center conductor length, which is just too critical.
And that's not the least of the issues. In cold weather in longer coax runs, the coax cable center conductor can contract and pull the center contacts in an N connection completely apart to the point where they don't even touch. Just imagine the SWR under those conditions!
I always used N connectors that 'captivated' the center pin. That's supposed to prevent that, but the captivating washers are made from Teflon, which can cold flow over time under pressure, and they don't fix the issue above.
I don't plan on ever using N connectors for anything below 220 MHz again. They are just plain unnecessary at two meters and below.
If you want waterproof connectors, then stretch-wrap the PL-259's with electrical tape after you fill them with non-hardening silicone dielectric compound to keep moisture out.
I've seen UHF connectors used at MF at the 10 kW power level, continuous duty (and W8JI says he's seen them used at 20 kW). I would never trust the flimsy N connector center conductor to hold up under those circumstances.
Check out post #11 by W8JI at http://forums.qrz.com/showthread.php?278609-How-much-power-can-i-put-through-a-BNC
and the comments by WB2WIK on a source for good N connectors at http://forums.qrz.com/showthread.php?269535-Coax-connectors