I have spent the last decade or so listening to ATCs every day for my work (I'm an audio engineer). I demo'd every speaker I could get my ears on before deciding. Genelec, Focal, Barefoot, Adam, etc. Keep in mind, these are all powered studio monitors. None of them were as smooth and flat as the ATCs. To my ears and in my studio at least. They really let me hear every nuance in my mixes and translated well to other speakers.
Having said that, several years ago the amps inside the ATCs starting making little hissing noises that eventually turned into intermittent failure. The tweeter would drop out. The woofers would buzz until I ran 100Hz tone through them at about 80dB.
I had them repaired. They had a few bad caps and resistors. And then it started again. Very frustrating. Turns out the building my studio is in shuts off the AC at night, the ATCs were getting overheated in there. And their amps did NOT like being hot. Especially this one little resistor. Anyhoo...
In 2004 I built a pair of Danny's AV3s for my home use. Then a pair of AV1s and a center whose name I cannot remember, but it's the AV3 with a tiny cabinet. I've been keeping tabs on GR Research for quite a while. When the ATCs started failing, I decided to rip out the amps and have Danny design a crossover for them. I bought some reasonable outboard mono amps for each channel and turn them off every night when I leave, just to be safe. I'm so glad I did this. Danny's crossovers opened up the ATCs even more. They're easily 20% better than they were. And I really liked them before.
Having said all that... The ATC / Bully comp is kind of an apples to oranges comparison for me. The ATCs being powered studio monitors that are meant to be played every day for years and years at near reference levels in a studio. And the Bully's are more of a "fun" rocking speaker with a passive mid bass / tweeter section.
But if someone held a gun to my head, it would really be a no brainer to go with the Bully's. The cost difference alone. But Danny's woofers and midbass drivers match or beat almost everybody out there. They're so light and fast.
I'm a little scared to bring my newly built NX Monitors to the studio for a shootout with the modded ATCs.
I can tell you that I MUCH prefer my AV1s (with Sonicaps) to our ATC SCM11s, which are also passive. And I use the AV1s for working at home.
My 2 pennies worth.