Mini USB of OK but there's enough out there where problems occur with micro USB.  Sure there are ways to deal with it but it becomes temporary.
  My Korg Microkey 37 still uses USB A.  My Novation minis have mini USB.  Unfortunately my IRig keys has a micro and it's the jack itself is bad.  If you are one who uses a small controller on you lap to mess around a mini USB wont cut it.  As long as manufacturers use a micro USB for connecting they are on my black list.  Micro USB is poor engineering. 

I'd have to agree! Not for audio gear specifically as I don't have any using mini USB, but I can certainly agree that the design for the connectors are just too flimsy for stable use. I'm experiencing that a slightly bent micro USB cable will NOT stay plugged in a port at ALL.
Mini USB isn't as pretty or small but it's a heckuva lot more stable and reliable - but then I'd rather go for USB-A if the hardware is big enough. But with the current trend of "smaller = better" I'm sure we'll only see devicing moving more into USB-C (which don't seem so bad) and more Micro USB since they've phased out Mini USB completely it seems.

I've bought 25cm right angle adapter cables for my USB devices with mini/micro sockets. The sockets are just too fragile for standard cables.
 

One other thing, there are substandard cables out there, too.  My wife's phone and iPad keyboard (charging port) will not connect with monoprice house brand micro-USB cables.  If I use a cable that came with a Kindle or her phone (I'm pretty sure its the kindle cable, though) it plugs in fine.
 
I agree though, for small connections, the lightning connector is a much better design.  And for audio stuff, there is almost no reason not to use a USB-A connector.  They don't need to be that small.

Funny, I thought the U in USB was universal, but I guess not.