Could you share your opinion/experience/preferences on this specific topic: MM450 vs IEM's on public transport?[/quote]
Just to give MHO I would take a good IEM anyday for noise but the comfort and such. Also heard from many that Bose's damping should be a bit better but thats is wired version that are not the same at all. I mean the MM450 even has exchangeable battery so you can charge one while the other is work as integrated AMP when you use the MM450 wired! But my IEM's and theses are Sennheiser so not even highest end stuff, MM80 I think, I always use for my smartphone for music as they can take calls with mic and then I have a comfortable bluetooth headset for support calls when grandma' can't get her laptop to work
In that respect the MM450 sucks a little since IEM's fit in your pocket by your smartphone and I often don't carry a bag to when out.