For what I see, whoever design the BTCGarden care more about quality and endurance than profit and did the boards design with more space between components and more heat sink cooling area making the miner to run cool, with less fan speed and noise making the fans to last longer.
What you mean by main bits?
That would be my thinking too. Thanks for sharing. Main bits was/is my reference to the ASIC`s working parts.
I have since seen some pictures, presumably of the BTCGarden board looks like they have Bitfury ASICs, but might be wrong.