It has 11GB total available storage. I have 5.83GB free on mine, but I do have TomTom and 738MB worth of videos that take up space. I have 1.28GB worth of apps installed. I haven't found the lack of SD card to be a problem (yet). If you wanted to keep your entire music library on the phone, that could be a problem.
I haven't tried OTG, but an external drive would definitely be a good place to keep backups. Now that you mention it, I might order one to try.
I don't know why they dumped the MicroSD card. Maybe planned obsolescence or they just didn't see the point since these devices are practically disposable since most people only keep a smartphone 2yrs tops before wanting to upgrade again. They started to do the same with Nexus devices too.
Oh yeah, and compared to the M, the battery life is a lot worse. I barely get 2-days of light use and I have Wifi set to turn off when the phone is sleeping and I also keep mobile data off when I'm not using it. I tried leaving Wifi on in its default state which is "Always On" and only got 1-1/2 days out of it. On the other hand, I don't notice the bad battery life so much now that I bought a wireless charging pad for $10 which works well with the Mini. I keep it at work and I just set the phone down on the wireless charging pad when I'm at my desk.
Last edited by GnatGoSplat; 7th February 2014 at 03:37 PM.