It sounds like you are testing calibration, which doesn't effect performance unless the the unit can't be calibrated at a certain temperature or perhaps through a range of temperatures if you are using multiple operating temps.
Comparing two stations that are not showing the same calibration or offset (which could affect recovery) would be a waste of time because they are heating at different temps. I've seen this mistake made in videos before, too many apples to oranges comparisons...
Shock, no. I am measuring the temperature when the iron is pressed to a specific heatsink. Then I'm measuring the no-load/set temp without the heatsink. But to take out any inconsistency in sensor readings (while holding the cold junction between my fingers) or other factors like heat sink temperature, etc, I went the further distance to swap irons back and forth several times to make sure I was comparing apples to apples best as possible.*
Calibration has no effect on this test. In fact, I did not even care what the display on the stations read at any point in the test. All measurements were done on the tip tester. (I only NOTED the final temp on either display as a matter of curiosity). I adjusted both irons until the heatsinked sensor read 200C. I had no idea which one was the winner until I tested the no-load temp. Whatever was on the actual stations' display is irrelevant. Only at the end of the test did I see the calibration was different between irons. But that does not matter and actually makes the test more valid, if anything. The 200C mark is a bit arbitrary. It could be anything, but keeping it practical makes the results more practical. Lead solder melts at 183-188C, and I figure you need to reach at least 200C at the interface in order to practically solder to a ground plane. And 200C is a nice round number that is easy to remember.
I do not claim the test to be highly consistent. It was a bit janky. Nor do I claim the 200C reading done on the heatsink and big blob of solder is absolutely accurate. This is not how the sensor/instrument was designed (but yes, the solder blob was mostly melted at this temp reading). But as a relative measurement performed side-to-side between irons, I am confident it is worth a lot more than empty boasts and speculation based on a single theoretical advantage with zero quantification.
What performance were you looking at?
Watch the EEV video, Soldering Iron Power Delivery Explained. This explains what I'm measuring: thermal drop between sensor (set temp) and the interface between tip and board when the tip is applied to a thermal heatsink. Notice that it is DAVE's test which is in all likelihood enormously affected (completely invalidated IMO) by difference in calibration between the two stations. When you set them both to 270 relying on the stations' displays, one is invariably going to be different than the other unless you won the lottery.
In my opinion, thermal drop is one of the main reasons why you have to adjust the temp on an iron to solder larger heatsinks/groundplanes. (But in reality, even if the tip could maintain set temp at it's very surface no matter what, you would still need to set the temp a fair bit higher than 189C, unless you only wanted to melt a tiny layer of solder on top of a blob). It is universally suggested that cartridge tips perform better in this regard, but my own experience specifically with 888 and T12 CLONES says otherwise. If there's a significant advantage to the T12 tip due to the cartridge sensor/heater arrangement, then there were other compromises made which nullify it. In fact, the "advantage" might need a negative sign in front of it. No, I don't have genuine T12 tips or 951 station.
FWIW, I have previously found the bakon and 888 to warm up in about 17 seconds from cold, using large bevel tip, anyway. Bakon runs at only 19.5V. 24.5V Suhan warms up in about 10 seconds. (I have also weighed these tips, and I don't have an exact figure because I don't have a broken tip to weight just the shaft. But based on the weights and the balance point of the T12, I believe the T12 version is less than half the mass, which adequately explains the difference in cold start times).
Yes, the T12 clones work very well. If I was in a country where the 888 cost $200.00, I would be pretty darn happy with T12 clones. I can't imagine buying a more capable station for $25 to $50. And I'd take almost any T12 clone over any 936/888 clone I have ever used. I'm just not thrilled when people parrot/promote marketing wank without any (appropriate) validation/testing (especially when it turns out to not be true/significant... possibly even a measurable disadvantage).
Warning. Physics ahead.
If you could get the sensor right at the tip, it might be significant. But getting this sensor closer to the base of the shaft on the tip doesn't appear to be that significant, to me, vs the conventional way. The main impediment you are removing is the bit of contact fit/air gap btn tip and sensor in the conventional arrangement... but the interface between heater/sensor and tip in the conventional irons is made large enough in surface area, and the sheer mass of copper between this interface and the base of the tip shaft where the cartridges get their "head start" is enough to do the job. The thermal resistance between the base of the stalk/stem of the tip and the actual working surface is going to dwarf any improvement that you can make in the back. IOW, even the theoretical improvement you can make is pretty close to squadoosh. In EE speak, you're moving your sense trace from one end of the 10 foot 0.5AWG copper cable to the other. But it's still on the wrong side of that 10 ohm resistor.
So if the difference between a power-controlled iron and a conventional temp-controlled iron is X, the difference between that and a cartridge is a very small fraction of X. At least until they can put the sensor right under the skin of the actual tip (without plugging up the transmission of power with the sensor/leads; talking micro/nano technology perhaps). The current status of cartridge tech is not there, yet. Does this lure look any better to the fish? No. It looks sexier to the fisherman. But don't worry. For today, we have RF stations. Aside from the marketing aspect, the manufacturers also win by being able to reduce the size of the heater/sensor-to-tip power coupling/interface. This means less copper needed for the manufacturer and faster cold start times for the consumer. But as far as thermal gradient/drop, the advantage is not necessarily expressed/significant/real/practical.
*What I recognize to be the significant factors in the test: tip surface area of contact with the solder blob. I used same 3mm TFO bevel tip on each iron and tried to get complete contact between solder iron and solder blob. I applied a dot of flux between tests, I was careful to keep the sensor centered on the tip, and to keep the tip level, and I swapped irons back and forth several times without shifting grip on the tail end of the sensor cold-junction (which did not noticeably get hot to my fingertips during the testing). Basically, I did the same thing, alternating several times between the irons, keeping everything as same as I could. I waited several seconds, maybe 5 to 8 seonds, until the temp bottomed out. As long as max power consumption is not reached (i.e. heatsink so big that the heater hits 100% duty cycle on one or both irons), I don't think there are any other important considerations. But if I missed something, let me hear about it.