Well I’m glad to have both, but if I could only have one at the moment it would be the Big Block.
I should mention that I have the standard version of the Acme DI, I have been curious about the more limited one with the NOS transformer but I can’t see how it merits that price ($1,100), especially when we have the option of the Big Block for less than a quarter of it.
I was very happy just running my preamp into the Acme DI. It may just be that it has more quality components than the XLR out of my Tech21 giving it more detail in the mids. Hard to explain but the while the low and high end feel very slightly mellowed/rounded out in a pleasing way, the mids sound smoother and clearer. Without the Acme, the mids just sounded more bloated.
On the other hand, the Big Block has options to get that mellow sound as well as the clarity, though I’m not sure about the exact frequency curves of both units matching on any of the Big Blocks variety of settings. What I’m digging most at the moment is the Big Block set wide open (both switches up and on the least attenuated setting). I don’t understand the science of it, how a passive DI can boost certain frequencies, but there’s more in the box than just a transformer.