Here is the side-by-side of the batteries. Luckily the batteries have their own markings so they will be easy to identify during this test. Note: Apple symbol on the eBay battery.

First step are to measure the physical dimension of each battery. This may seem tedious since it was done for each battery but for the integrity of this test its deemed necessary.

First the iFixit battery. Weight is 42.79 gram

Length is 108.82