Originally Posted by CarbonJoe

5000 mAh 40C are fine for 17.5. Most of the bigger C discharge ratings are difficult to reach, regardless of the battery companies' marketing claims. As far as brands, most if not all of the cells are made in China, so purchase from a label you feel comfortable with. Because in the end, the package dimensions and label are all that most "battery" companies really design.

There is a thread on here where the owner of SMC tested a bunch of manufacturer's batteries, and the best were really around 40C, regardless of the sticker on the pack. Take that for what it's worth.