They are a touchy subject on here mate.
I would personally steer clear of them. They are illegal for one. They also dont give the best light output and will most likely blind other drivers.
I did look into them but quickly decided to go with genuine R xenons! I am glad I did! The difference between them both is the ones you are looking at will be used in a reflector headlight (used for halogen) but genuine xenons are projector headlights. With the genuine you get bi xenon as well which is xenon for both low beam and high beam (as well as a halogen bulb)
The light output on my xenons are nothing short off fantastic. The full beam lights up the road like daylight. Also I never get flashed after having them aligned properly!
I am not sure you will be able to say the same for an aftermarket HID kit!
Ultimately it is your decision but for not to much more (i paid £320 for everything) you could get the real deal which are excellent.
Hope this helps,
Ollie