Except all the answers are telling you why it's not a simple answer. The analyser only tells you how it behaves without a load. To know which one to keep, you need to know how they perform with a load.

And with a load or a real dyno the current will be that high that it is better to solder the wires fot a reliable measurement.

I give up

Not a complex question, sure - but it’s a complex answer if you just go by the simple data he provided. So yeah, pick the one pulling less amps, but then if he has to drop two or three teeth to keep the car from being a total dog compared to everyone else on track, then what did he gain by simply choosing the motor pulling less Amps?

Conventional wisdom says a mod motor (high rpm) geared lower will out accelerate a spec motor while also having a higher top speed, but if you can prove otherwise I'd love to hear how. A high RPM motor geared lower gives better acceleration.

I've got an outlaw 17.5 motor that runs a mod rotor, and I would still gear down significantly going from that outlaw 17.5t to a 7.5t motor.

Sure...
Not always. The OP has two motors of the same model, not one mod vs one spec. That comparison is irrelevant.

Without testing the gauss of the rotors and the internal resistance of the stators there is no way to know (aside from putting a load on the motors to see how they perform). Considering that rotors are made in batches and most stators (in rc motors) are hand wound I would venture a guess that the motor pulling less amps has a lower internal resistance, in which case my point stands. He should switch the rotors and see if the performance changes.

Have you ever run a mod motor on an analyzer? You can make a mod pull less amps and more rpm than a spec motor pretty easily.

Lastly, depending on the application a weaker rotor does translate to faster lap times, that's why there are tuning rotors. I've run that same outlaw 17.5 motor with a 1/12th scale 1s specific (high rpm rotor) and it worked great in a 1/12th scale car, but didn't do as well when I tried it in a 2wd buggy.

If op switches rotors between his two motors it will give some insight into why the two motors are pulling different amps.

Cleanly solder and you can still sell one, may be for a few bucks less but that way YOU will clearly know you made the correct choice ... that will be the only way to determine in YOUR application which will suit your needs the best ... asking which will be the 'best' for you to keep with the info given is going to be a cr@pshoot at best, too many unknown factors here to make the call in YOUR 'real world' scenario ...

JMHO, as usual ... ;)

That's the whole point. The analyser can't tell you these things.

I have. The stator is vastly different, so making it perform differently is moot. When you put an actual load on the motors though, the mod motor will still pull more current.

That's why I said "not always". You stated it as fact like it was universally true.

I just got off the phone with Ron Schuur of Schuur Speed and he said there is no way two brand new motors would pull those different amps because of the slight manufacturing differences between rotors. He said the only explanation is that the stator in the one pulling less amps has a lower internal resistance. He stated the motor pulling less amps is the better motor. I trust what he says as he literally sets up locked timing motor batches for spec classes at big races.

If you want his phone number I'm sure he'd love to talk to you about it.

BOOM!!!!

Well, based on that answer then, I wouldn’t keep EITHER motor, because if a stator is not supposed to have that much variance, the company that made those motors has a serious quality control issue if one had a lot less IR than the other - assuming they are two of the same motor - but then, we didn’t get that info, did we?

Agreed. Stator variance is far easier to keep consistent than rotor variance. You'd need a hugely defective stator to increase the current by 50%. The two components with the highest variance are the rotor or sensor board. The latter can actually be checked by an analyser.

They are usually budget motors, which means the QC on them is quite lax. That is the precise reason race promoters have Ron Schuur ensure equal performance among the handout motors for large events. I have a backup Nats motor from Paul Lemieux. He runs Motiv and this was likely the second best 13.5 of all of them that they went through. The motor is insanely quick. Early HW fixed timing motors had about 25° of timing while the newest ones have about 45°. My logic with motors is the fastest team drivers are going to get the fastest team motors. If I buy a regular, never checked motor it might be one of the really good ones that slipped into jon q publics hands. The other thing is being able to use the extra power. If you can keep it on the wheels and drive a clean line, it makes a difference to have a nice motor.

All things being equal, keep the motor pulling less amps at the same kVA / motor that needs the least timing to get the kVA.

even if the rotors are, say, 1500 vs 1550 (a common spread on some motors) you won’t see 50% more amp draw at “zero” load. It will unlikely be 50% less current (actually, can almost guarantee it) but it’s a definite sign of efficiency difference which will result in lower battery drain.

the motor pulling 2A, set it to 3A and tell us all what the timing and kVA is.

in essence you will get a guide of efficiency then, how much extra RPM you will get for the same current draw.