Thanks for breaking it down so well. I like how the white version looks (and the price too), is it a lot softer than the metal?
Sure, no problem.
I wouldn't hit someone in the head with any of them that's for sure - they're all solid and well built (like everything Xiaomi). But the 4.2 white one is an aluminum frame around the outside edge and plastic covers on the front and back, whereas the "metal" one is full aluminum body except small plastic panels on R and L side.
The silicone skin cover for the metal one gives the "softest" feel to any of them though.
You really can't go wrong with either IMO. The new white one is 1/3 less cost. So if you want a good quality speaker that sounds great and has the maximum battery life (10 hrs), get the white 4.2 one. If you want sdcard playing, slightly deeper bass, and an indestructible build that could survive a car crash, get the metal one (8 hr battery life). Both are excellent choices (I wouldn't recommend the original BT 4.0 white one though; the bluetooth on it can be problematic at times).
I personally think Xiaomi is phasing out the metal one, because they took the best features of the metal one, and incorporated it as improvements to the original white one (ending up with the 4.2 white one). Why have 2 similar competing models, when you can just have 1 nice one? The metal one is just redundant at that point. Honestly, if they had included the microsd card slot in the 4.2 white one, I wouldn't even had bought the metal one.
And it only comes with bluetooth connectivity compared to bluetooth / AUX / TF for the metal?
The new "white" BT 4.2 one does come with AUX (sorry I didn't clarify that earlier), but no microsd slot.
Also, be aware that the language on all of them is in Chinese (the manual and spoken announcements). So instead of hearing "pairing", "low battery", etc all you'll hear is some lady speaking in jibberish unless you speak Chinese. The functionality and operation is very intuitive though, so the language doesn't matter.
If you get one and have any questions about how to do this or that, just lemme know and I'll get you squared away.