cyanyde,
The Tamiya BL system with 12T BL motor, which looks like a rebadged HW is equivalent to a 23T brushed. This would not be accepted by our rules here in Aust to run in the Mini class.
During trials for a acceptable BL system for mini a lot of different BL motors where tested. We found that the 3300Kv motor was to fast and that the 300Kv motor was competitive with the sport tuned motor, without the difference in RPM variation. Forget 17.5 and 21.5 in a mini, as these are slower than a silver can, even when fitted with a 20 tooth pinion.
We have a set of Mini rules which have been accepted by QLD, NSW, VIC, Tassie and SA. I'm not sure about WA. So this has made running mini class the same where ever you decide to race.
The growth of the mini class has been seen at every major meet this year. Nine times out of ten, Mini is the biggest class. The biggest reason for the larger numbers, all cars are equal in top speed, due to the use of the control BL system. Now it has come back to driver skill and car setup.
At the end of the day, run what you are allowed and if you want change then vote for changes to your rules.
Good luck, Happy racing.
Calvin.