Given the same speed/torque numbers, is a brushless servo always better, basically the same, or actually worse than a coreless brushed servo?

It all comes down to response speed. Obviously they're the same speed over a fixed distance given the same ratings, but that says nothing about how quick they start moving or change direction. I have a coreless and 3-poll servo that have basically the same speed ratings and you can hook them up at the same time and see they both are just as fast at sweeping back and fourth, but the coreless is dramatically quicker at changing direction and you can actually make it jitter and wiggle where as the cored 3-poll can't keep up at all.

My gut says that brushless is at least or better than coreless in terms of response, but I can see companies selling something that is actually a little worse just for the use of a popular buzz word. The only advantage I see on futaba's page is thaty they last longer than brushed motors.

Compare the futaba s9351 and bls452. The coreless 9351 is .13/192oz and the bls5452 brushless is .14/194oz, but the coreless is $20 more! Both are metal gear ball and bearing. The brushed coreless has a metal case, but then again, the brushless is supposed to run way cooler so perhaps it doesn't need it. The 9351 coreless is also dust/water proof, but is that worth the $20 difference, minus of course the fact that the other one is brushless?

So what's the deal here?

IMO cars and trucks don't put the demand on the servos that would truly show the differences. For instance, Brushless would be great for a Heli rudder servo because of the constant input from the gyro... less heat equals more efficient and less likely to fail. Water resistant means fine dust resistant, too. I would go coreless before brushless in a car/truck... What are the input voltage capabilities/requirements... is that important for your application?

It's really just a general question really. I run 1/10 ep and 1/8 gp/ep, but the question isn't really for my application as much as just in general.

I'm no expert, by any means, but it seams to me that the motor in a coreless motor servo is very similar to a brushless motor anyway. And, the position sensor and the receiver resolution has more to do with servo accuracy and precision. I asked the amp draw question partly because I was curious if there was a difference in their required amps for best operation. You ask a good question... now I'm wondering if there is a difference in holding power, or maybe amp draw during max load... Don't know, I'll have to look into it.

Futaba says Brushless are 5x longer lasting than brushed servos and respond 30% faster(faster than what it doesn't say), all with same power consumption... I don't think I've ever had a servo go because the motor brushes failed, so 5x longer lasting means nothing to me. 30% faster response time is probably dependant on receiver resolution, battery/BEC voltage, and application. So I still stand by what I said before... Brushless is Good for heli's and other high-demand/constant imput applications. For Cars and Trucks I'd put emphasis on torque, speed, durability of gear-train, and dust/water resistance like you said... No advantage to brushless in surface applications IMO

1/8 offroad steering servos are pretty constant heavy usage I'd say. If the car is driving, it's trying to hold the front wheels of a 8lb car the right direction while putting generous portions 2.5 hp down through those same wheels. That servo's always got stress on it unless it sitting on the box warming up.

Oh, okay... so now it IS a specific application... whatever, man... buy what you want.