worth it

So I've been looking into a 7x7 cube for quite a while now, and I'm torn between 3 cubes. Would anyone mind telling me which one is the best (and worth the money)? 1. The V-Cube 7 ($50) 2. MoYu AoFu 7x7 ($50) 3. ShengShou 7x7 ($20) Thanks, Cubemageddon