I suppose anything with a reputable name and review on amazon. Going too cheap (1-3$) on ebay may risk causing electrical damage with poor components and voltage protection.
The motorola seems to have the highest reviews/sales with 4.5/5 stars. I think I might head in that direction, especially since it has a quick charge rate.
The Anker also looks good 4/5, with the additional USB connector for passenger plugin. I've had decent exeperience with the extra USB slots - however did blow a few internal fuses.