I got to try both demo units of the B300 at the 2nd day of the meet, and at least for that short listening session I couldn't hear any difference between the two. My take was the B300 was more neutral than the slightly darker learning B400, but as recent commentators have mentioned this could also have to do with eartips.
I would also like to mention how great the build quality is and how EXTREMELY comfortable they are to me, even just the demo unit! These universal fit IEMs fit my ears like a glove and seem to have a perfect seal, even though I have an ear-shape that doesn't agree with most IEMs. These IEMs use tips with the smaller diameter nozzle and the ones on mine were medium black silicone or rubber tips which fit / sealed perfectly. Though after trying almost a dozen tips from previous IEMs (including Spinfit), I settled on a medium size rubber pair of the double-flange type that seemed to up the impact and overall resolution for me.
I would also like to mention how great the build quality is and how EXTREMELY comfortable they are to me, even just the demo unit! These universal fit IEMs fit my ears like a glove and seem to have a perfect seal, even though I have an ear-shape that doesn't agree with most IEMs. These IEMs use tips with the smaller diameter nozzle and the ones on mine were medium black silicone or rubber tips which fit / sealed perfectly. Though after trying almost a dozen tips from previous IEMs (including Spinfit), I settled on a medium size rubber pair of the double-flange type that seemed to up the impact and overall resolution for me.