Just a matter of personal sound preference, rather than which one better "H" or "A". What I was trying to say, RE300H and RE300A I have in my hands and in my ears sound VERY CLOSE. If you don't like sound sig of one, switching from A to H or vice versa not going to change anything. RE300x is about bass and clear sound with a super isolation (granted you are using the right set of tips); it's not about balanced detailed sound.
Regarding burn in, it all depends on the type of the driver and cable wiring (quite often dd will change, and you can have an affect of solder joint and wire burn in when its a silver-plated wire), how you are running burn in (brain burn in while listening, or 60hrs in free air), and the quality of your hardware source and audio files (your ears will be more sensitive to changes with a higher quality lossless files and higher resolution DAC), etc. I tested dozens of headphones (gotta be easily over a hundred), and some had very subtle difference after burn in while others were night and day. Take for instance the latest T2 - out of the box and 10hrs later - like two different headphones, you will never believe you are listening to the same pair in a blind test. On the other hand, effect of RE300x burn in was just in tightening of the sound, nothing drastic.
Regarding packaging and extra tips, I was just guessing since RE400 and RE400B (bundled with HM700) had a nice packaging with fancy cutouts to display eartips. Sure, they could have easily put a few more pairs in that little clear bag, but I think they are really focusing on the included universal double-flange tips, even feature it in the graphics of the packaging. Again, I'm just speculating since HiFiMAN really likes to pay attention to details, and a lot of other Chinese manufacturers pay attention to HiFiMAN copying it lol!!!
