I use a Nikon Battery Grip on my D800 and a Promaster 3rd Party on my D7100 - Although the Promaster is fine, it works, I have had no issues, it just feels cheap. The Nikon battery grip light years ahead in quality.
If you don't have the money the 3rd party will be ok. I would now only buy Nikon or not at all.
That pretty much summarized the difference.
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