Had the Canon grip on my T2i, and the Vello grip on my 6D (I've not had any issues with the Vello in 2+ years). Power is not a concern for me, yet I do keep two batteries in the grip. My main reason for having the grip is to balance out heavier lenses. It just feels better shooting handheld with the grip than without (big hands maybe?). I do also like the portrait controls.

Matt