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.
Simplifying Comfort (...a Better Power-cord)
We have been making this pretty neat coil cord power control for twenty years. I remember designing it to be an illuminated hi-low inline switch of such small dimension that it would not be a 'lump' in the middle of a compact coily power cord. We went round-and-round trying to find a switch which would allow a better functioning and packaging design. Something tactually, visually, and ergonomically lighter and cleaner.
And there still isn't anything as good in terms of simplicity and overall handy-ness. I wanted this cord switch to be so easy to use one could forgo a thermostat. They always seemed useless over-complexity...even the newer nice digital ones everyone uses now (just yesterday all were stupid power-hungry inefficient resistance rheostats). I'd used one several times but wanted something thoughtlessly simple, super-compact and field-reparable if ever needed. (This last consideration turned out irrelevant.)
It's just too easy to be riding along and without looking down move my left hand downward from the grip momentarily to find the cord lying across my left thigh and then by touch alone (finger or thumb) push or release the illuminated in-out button…then move my hand back to the left grip.
It's only one second, done without thinking, and there's no fumbling around. I can feel at a touch if the button is in high or low position to maintain temperature at a nice level all day long, with neither thought or effort. Just click-on and click-off as needed for comfort, and if there's ever question about power status a quick glance down shows the red pilot light glowing on or off through the button's cap. Even in daylight.
So today if I were for some reason forced to use some non-Aerostich electric garment, I'd still want this simple, intuitive and reliable coil cord and switch.