IMHO, the BMW one is overpriced. There's a big selection of available units. A basic one only has 4 indicator lights. A fancier one may have a power readout/voltage readout/internet connection/remote control functions. If you want any of those extra features, you will pay a bit more.
I have a Clipper Creek unit that has been working fine for close to two years now. Made in the USA. Most aren't. The only thing I've heard is that on some, if you have a power problem (power outage), some units will not reconnect properly without unplugging and then replugging the cord.