I'm gonna say Moyu, though YJ is pretty close.
Moyu has made:
- The gold standard for budget cubes, the RS3M 2020
- The WRM series, which are amazing cubes for a very manageable price
- The GTSxM series
- A brilliant 4x4
- The largest produced cube (21x21)
YJ has made:
- A great 2x2
- A pretty good 3x3 with the mgc elite and the mgc evo
- The best 6x6 on the market by far
- Amazing 4x4, 5x5 and 7x7 cubes
- The best Squan on the market by far