I can share with you my opinions that I have formulated after asking myself very similar questions for the same reason as you. At a certain point I felt that whooping should be pushed to the next level (brushless) after feeling like I had found the limits of brushed durability and performance … and wanting more. However, I still have not jumped in on a brushless whoop so these are the opinions of someone that is holding back after doing research - and has not tried it yet. I do plan to build out one just to see if my guesses are right.
I believe most accounts of 0703 burning out are from prop strikes that momentarily stop rotation, cause current to spike, and toast the windings. A good portion of them are assumed to be DOA but likely were killed by a winding breaking during handling through the build process. Conclusion - windings are weak.
11xx motors are very durable. Most accounts of winding failure during handling and physical construction failure during crashes are from racerstar 1103 1st Gen. And I myself do own those and 2 other flavors of 1102 which have survived nothing short of punishment. Bearings in my 1102 seem to be the first thing to go south.
Motors themselves aren’t the source of noise - it’s the props you put on them, the rpm you spin them up to, and how quickly the motor can change that rpm. I’ve not tried any props smaller than 57mm on brushless but some of them scream like the world is coming to an end and others are oddly quiet.
The main reason I don’t fly anything inside but a standard 6 or 7mm whoop is that after much of my own testing - I came to the conclusion that a whoop is just the perfect tool for the job. I even built a 6mm craft that weighs 2 grams less than my whoop, has no ducts, and put 46mm props on it for a bit more grip and power. Result - I created an outdoor craft that was too loose around corners and too fast to really enjoy inside. Conclusion - the ducts, the prop size, and the all up weight come together in a whoop to make it the perfect indoor craft. If you’re gonna go brushless - make sure you keep all three of these things constant - same as a brushed whoop… or it will not whoop. It will just be a tiny outdoor craft.
At the end of all my experiments to change something about the whoop we know and love to make it better - I came to essentially one conclusion. To leave it alone. I actually reverted a bit and really enjoy my 6mm whoop over my 7mm whoop cause it just handles better (less momentum). That said I did uncover one super secret key to ultimate whoop performance - the only thing that should be changed… and it’s the height of the ducts. I have printed and built hundreds of variations on whoop frames and formats. When duct height is limited to about 6mm - performance skyrockets and handling (the ability to whoop and feel like a whoop) seems to remain unchanged. This is the only variation on the whoop format left to be discovered by the “mainstream” in my opinion. I hope to find both the time and the right design and material to make this 6mm duct height frame possible with the same durability we have come to expect in a manufactured frame. Time will tell if I’m successful.
Back on topic of a brushless whoop though - I will go 0703 (maybe 0705 if I can get weight right) on 1s with stock whoop props and a frame that resembles the standard whoop frame in an attempt to keep weight similar, props the same, and the ducts the same because without those three - it will fly but it just won’t whoop IMHO.
Happy new year my friends!!!