Which power connector?
If you have a BMW with a built-in BMW accessory socket, then the BMW-style connector is simple, easy and good. Otherwise we recommend the Quickconnect, also known as coaxial or 'male-and-female' style. It's the easiest to use (to connect and disconnect) and has lowest electrical resistance, so your gear heats up a little faster. (A nanosecond? Half a minute? In use we can't feel any difference, but we once did some controlled bench tests and there is a difference.)
There are zero reliability issues with all styles. All are tough and durable in all weathers and conditions. The SAE (Society of Automotive Engineers) style is the commonest and oldest design, and it's the hardest to push together and pull apart, but this gets slightly easier as it breaks in. It's also the least expensive to manufacture, and is the most widely available at auto parts stores.
The BMW style has one feature the other two don't...It comes apart with a screwdriver. Inside are two little set screws, one holding each wire to it's respective terminal. These make it simple to transfer the plug to another wire if anything does break. This style is slightly larger and bulkier, and by a small margin it's the easiest to manipulate wearing bulky insulated gloves.
But we still prefer and recommend the durable, compact and easiest-to-use Quickconnect coaxial style. Overall, it's the best.