I have quite a bit of experience with 4x4s, and I would recommend the DaYan+mf8 due to being half as much as the X-Cube, it is the world record cube, if lubed and tensioned it is amazing (but tensioning will be necessary to reduce pops). It is also one of my favorite 4x4s. But, if you have the money ($40 dollars to be exact), and are willing to do some lubing and a lot of tensioning, try the X-Cube. Finally, on another note, for questions like this you should ask it in the One Answer Question Thread rather than creating another thread.
Hope this helps,
Ian
P.S. The QJ Mini is a pretty decent 4x4, considering it used to be the most popular before all of these new screw-spring structure 4x4s