USB or MIDI? Is USB dependable?

[ChSys]

I get nervous using my KeyLab Essentials 61 with  Logic Mainstage in live situations.  I set everything up, starting Mainstage after all connections are made. MIDI is responding in the top center window of the program. Keys respond on the virtual keyboard on my screen. Yet I get no sound. Panic! If I'm lucky, I can quit Mainstage, and try again, and this time it will work.I'm confident Maintage is set up correctly--I don't think it is a problem in Mainstage.    Mainstage Users Facebook page advised that MIDI pin ports are more dependable and are what the pros use live.  They advise against USB connection.  I switch out USB cords, with the same undependability.

In general, I'm not sure whether using a controller  is advisable in live situations, in case of a Mainstage crash.  Perhaps using a keyboard with built-in sounds as backup is preferable.  Your thoughts on this as well?

[MajorFubar]

I have never had any problems using USB connection from controller to computer so I'm probably not the best evangelist for legacy ports like midi sockets. The only time I ever found MainStage unresponsive is when I had accidentally changed the midi channel on my controller. This might be your issue, or it could be something else, but if the keys are responding on the virtual keyboard on screen but no sound is coming out, then clearly you can rule out the USB connection because midi data is obviously being transmitted.

Unless your computer has a built in midi interface card (which I'm guessing it hasn't, seeing it's a Mac), one way or another your controller will still link to the computer via USB, either using a direct cable from the controller or through a USB-to-midi interface sat between them (be that a separate box or a cable with the USB-to-midi electronics bodged into it somewhere). Either way, IMO, adding another piece of hardware between the computer and controller is just something else waiting to go wrong at a critical time, and you're better off with USB to USB. I'm sure other opinions are available, but that's mine.