Adam - I really like the BK. The BK is pretty efficient. It pulls out in 2 days what the ER would pull out in 3. My water column also looks clearer now. The BK is well built and silent.
Would I go so far to say that the BK is worth $1000 more than the ER? Probably not. It's like asking if a McLaren SLR is worth 300K more than most cars. You buy it not only for its performance, but for other features, build quality, etc. part of what you're paying for is its name, too.
My ER was a great performer with the Eheim 1262 on it. It, too, was quiet. It was not much louder than the Red Dragon. However, it pulled much less air at much more wattage than the RD.
For 8 years, I used only ERs because I never wanted to spend that kind of money on equipment. For some reason, I had the itch to give a high-end skimmer a try.
Would I buy a BK again? As long as I am willing to spend that kind of money, a definite yes. If I did not have the "itch", I would still be very happy with my ER.