I was considering the Pixel Vertax BG until B&H released the Vello (recently). I'm only waiting for some reviews on Vello's before I make my decision since there are only 4 reviews on B&H. At least they dropped the price ~$20 this week, At least I waited since last week.
Reference- (http://www.bhphotovideo.com …o_BG_C9_Battery_Grip.html)
It looks good in the pictures but thats basically all I can conclude.