|UV- and water-proof|
MC4 connectors are the industry standard for solar power and they are rated for 20A at 600V. Unlike Anderson Power Poles, MC4 connectors are waterproof and snap together with a pair of barbed inserts.
They are also much easier to install onto wire. I am using 10g stranded copper for the run from the panels on my roof to the indoor charge controller and the connectors have gone together without a hitch - much easier than APP connectors.
Each contains three rubber o-rings: one on each connector-to-wire fitting and another joining the two connectors (male & female) together.
Any time I've ever used APP connectors, it's been because I've had no choice. They have their place and are fine for indoor applications of stationary radios. But for mobile, portable and outdoor use of DC-powered devices, I'm going to give serious consideration to MC4 connectors in the future.
Here's what Wikipedia says about them and here is a video demonstrating their installation: