Found a few posts out there suggesting that the 8120 and 8150 are identical (with a little tweaking) and there was no reason to purchase the more expensive model. Is this true?
All the answers and no explanation.
In semiconductor manufacturing, a huge chunk of the cost of making processors is designing and making the mask, which only needs to be made once. This means that there typically are very few different chip models being manufactured at once. For example, on Intel side the cpu models i5-{2300, 2310, 2320, 2400S, 2405S, 2400, 2500T, 2500S, 2500, 2500K} and i7-{2600S, 2600, 2600K, 2700K} are all the exact same chip. At present, actually every single FX cpu is the same chip.
However, not every cpu made of the same mold is identical -- some run at higher frequencies, some can function at very low power, some leak more (so they run hotter), and some have manufacturing errors. This means that after being produced, chips are
binned -- that is, they are tested and sorted for different products. At this point their clock speed is set to something, and if they have faulty cores, they are turned off. So, purchasing the higher model number would presumably get you a chip that's from a bit better bin. Realistically, given how little difference there is in the stated cpu speed of the chips, this probably doesn't matter.