I haven't ever done a direct comparison, or used either mic myself. But from many stealth tapes I've heard, I'd go for the 4061's over the Sonics in a heartbeat. You get a nice full sound from the 4061's, the Sonics sound like a stealth mic to me. Bo good to have some way to roll off some bass with the 4061's as they can be a bit bass heavy.
word about the bass. armen, any word on the BB mod for roll-off?
Thing with the bass is, the 406xs capture all the bass at a show with no problem, where Sonic Studios and many other mics will fail because of it.
This also means that you have to watch what you run the 406xs into:
An AD-20, for example, or a recorder mic pre? Brickwall city.
Line input? It's all butter.