I have a TP-Link TD-W9970 and a Zyxel VMG1312-B10D.
TBH there was very little between the two when it came to line performance. Obviously though with the WMG1312 using the standard BCM shell, it gives it an advantage when it comes to harvesting stats. Both give slightly higher downstream than the HG612, but sacrificed some upstream.
Both are pretty good value for the money, but neither perform as well on my line as the VMG8321-B10A which has the better chipset - which incidentally is the same as in the VMG1312-B10A
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My VMG1312-B10D was a new ex-Zen model. Its was very easy to flash using the latest f/w that I obtained from the Zyxel website.
You can easily identify the B10A -v- B10D by sight alone as they look very different. The B10D is the upright model.
B*cat is correct - Zen only supply the VMG1312-B10D.
NS is correct - the B10D has the budget BCM63381 chipset, hence why both the TD-W9970 and VMG131-B10D retail so much cheaper than those with a BCM63168 chip