I bought both from Q-Windows (what it was known back then) and from China. Each has their own qualities and I would say both performed well for the tasks that I wanted them to.

For me, the take-home message is to find out what you want your windows to function as? Soundproof, will need double glazing but if your wall material not that good, the sound will still pass through.

I choose Q-Windows for their European-styled tilt and turn window and also for the soundproof function.

As for the China ones, that's because I needed a bigger sized window for viewing purposes.