Audioguru was being excessively dramatic about the effects of discharge rate on cell life, you are definitely not killing the batteries, though a lower discharge current will always result in a longer cell life, especially in battery packs (not just single cells) RCinFLA's value of .5 to 1C sounds perfectly reasonable to me.
A ran for approximately 82 minutes, and B ran for 70, that's a ~13percent run time difference, again that seems high for manufacturer variance, right up until I looked up what Hi-watt is, which is a Hong Kong based battery maker, for cheap made in china batteries +/- 20% capacity difference between similar packs wouldn't surprise me in the slightest. If you want a multi cell battery pack to last any length of time you have to use high quality well matched (same capacity) cells. The cells you're using are going to invariably lead to an early pack death significantly faster than if it'd been made from quality cells.