Newton, Custom, and RRS are all pro grade products much loved by working pros. These are listed in order of increasing purchase price; all are $200 or higher. Newton and RRS are both light weight and sturdy. Custom tends to be heavier. Note that Custom has two versions of the same fundamental design, and one version forces clockwise rotation of camera to Portrait orientation, which is suboptimal for anyone who likes the supplemental control buttons found on the Canon battery grip.
Brackets less than $200 generally have some deficiency in design which makes them suboptimal.
[edit] One forum member 'called' me about the rotation, and I checked and he was right. Both versions of a single design are right handle vs. left handle, but use the same camera rotation (CCW) in both cases!