Wanscam has almost always been my favourite brand of IP camera except for the unfortunate HW0036 experience.
I have a bunch of them (HW0026, HW0049 and HW0046) running 24/7 and are still fine after 3 years.
The K21 looks identical to the HW0021, but with a full HD sensor, and a face detection feature.
Another noticeable difference is the price, and surprisingly it's actually 15 to 20$ cheaper than its older variant.