Good to see we recognize that not everybody hears the same way, hence the value of diverse opinions on forums like this. Given that (most) IEMs in general don't 'scale' as much with higher amps as do many headphones due being more efficient (correct me if I'm wrong), and the fact that it's debatable at best whether balanced armature drivers change over burn in periods - to me IEMs can pretty much be taken at 'face value' so a fairly reliable impression can be had in a shorter time; that is of course given they are properly driven and with good source material. 'Brain burn in' can actually make one more akin to liking a certain earphone, but what can I say - I already have something to compare it directly with that sounds to have a few advantages.
In terms of BA drivers being quicker than dynamic - perhaps as in a faster decay, that's interesting and something I could look into. Possibly our meaning of transient response differs, because I interpret this to mean the speed in which a change of volume occurs from... say 0 to 80db for instance, which is the initial 'attack' of the ADSR slope so essentially the largest influential factor in dynamics. You did mention that BA drivers suffer a little in dynamic impact, and maybe this is why I've interpreted them in this way, but to me 90% of all BA's sound muddy. I'm not much of a BA fan, though I have heard some expensive ones with 6+ drivers that sound almost akin to the HD-800.
We may also have different definitions of imaging, which to me refers more to stereo width, but I see you're referring more to elements within the soundstage, so this is something I can update later on the review. The B400 definitely has imaging, and oddly I didn't even notice anything amiss with it until I was done with my usual headphone test tracks and gave it one last go with some experimental noise tracks. I have a lot of white-label recordings ripped from live public radio broadcasts of abstract noise and field recordings, and when listening to one it struck me as the B400's having a somewhat 'off' quality to the imaging (or in my sense 'stereo width'), whereas with another of my IEMs sounded very natural in this regard by contrast.
Per my scoring method, I'm all about sound quality and put little emphasis on look, price or value so my score was purely for the sound.
Though many more, here are the main test tracks I used, which I have chosen because to me they seem exceptionally well mastered and have many elements to focus on such as hard-hitting drums, complex layering, soundstage, etc.:
Karsten Pflum - V.A.S.T. (very good for testing sub-bass with the intro, and my mainstay for dynamics with its' drums)
Bruce Springsteen - Tenth Avenue Freeze-out
DJ Shadow - Def Surrounds Us
Spice Girls - Stop
Wheatus - Teenage Dirtbag
I can update the review with these 3 things a little later.
I may be more of a critical listener - a perfectionist on a quest for the ultimate sonic purity, so my reviews may seem a bit meticulous or even ruthless, but with an aim at exposing weakness and spreading tips for the betterment of both innovation and community knowledge. I did have some helpful discoveries with both the B400's as well as other insights that may be helpful for anyone that also wants to read my review.