That's exactly the game they're playing with their specs. they quote the low power J/GH trick... without quoting the performance... and then somewhere else they quote the performance, but are not quoting it for the low power mode. What you want is a categorical statement as to what performance it hits at what power consumption for each of the modes... and they've never supplied that! Probably because they have no idea what the performance of it in low power mode will be. And whatever performance it gets, so will everyone else.. because reducing the voltage on a chip isn't new. its just not economic to do it, as everyone wants max performance, not min performance for their dollars!
Mostly though my point was that packing 300W into a single chip sounds to me like a major challenge, and IMO is not a good way to go about making a miner chip.
I guess the proof will be in the pudding.
Cooling four 300 W chips is kind of straight forward as they're in the ballpark of what high end enthusiast over-clocked intel chips clock at... thus theres a wealth of cooling technology that fits the bill, including the liquid cooling that cointerra (and hashfast) are using... and also, air based coolers with giant metal heatsinks like what KnC are using (Arctic A30).
Whats not clear is that if you need Forty 30 Watt chips to do what Four 300 W chips can do, to both yield 2 Terahash in a 4U box... then its actually a much harder problem to cool 40 chips than 4... as those 40 chips will still need something much better than regular air cooling.. and each chip may need its own heatsink.. or, one huuuuge heatsink that covers all 40 chips... etc etc..
Its probably easier to cool 4 hot chips because you definitely know where the heat is coming from and can use liquid to move it to the outside of the box... whereas with 40 chips the heat is coming from everywhere, spread out.. and not easily contained. You're relying on AIR to move it to outside of the box, which may actually be more difficult. Liquid moves heat much more efficiently than air.
as you say, the proof of the pudding will be the cooling. whose cooling solution works better is going to be the critical component of comparing these two designs... as well as cost. so far, for january prices, cointerra's is half the price of bitmine's. presumably for feb prices too, cointerra will be lower cost.
Having four big chips is probably cheaper to manufacture than having forty less big (but not small) chips. its a bigger board, (actually, its a lot of boards, each with a bunch of chips on it.. 8 per board?) with more dc/dc converters, and more 'chip packages' and yet its the same total power consumption and total performance. Whats worse, they're all daisy chained together!! one fails, they all fail. like the old fashioned christmas lights.