virtual ground used as ground in all circuit??

I've seen some audio schematics that connect, for example, input and output jacks ground pin to virtual ground.

Using +4.5V, 0V(gnd), -4.5V

Some examples:

While other schematics use virtual ground just for the op-amps, and then everything that needs to connect to ground is 0V. Using the same ground as the 9V supply
Using 0V(gnd), +4.5V(virt gnd), +9V

Example:

http://www.tonepad.com/getFile.asp?id=98

What is the advantage/disadvantage of these options? Is the same thing?
I would like maximum output levels and typically use TL072 for output op-amps.
Made some designs that work well in Arduino, some PWM oscillators, also made a AY-3-8910 synth and always using the same ground as the 9v supply.
Thanks!

It depends on the particular circuit. If the power supply is totally isolated you'll generally be OK and you can connect the "isolated" floating ground to an external "true" ground.

With a battery, the + & - battery terminals can both be non-grounded so your local virtual ground can be connected to true ground.

If the power supply has a true ground, then you need to be careful about connecting the virtual ground to the outside world.

There can also be current limitations. In your op-amp circuit, the 2K resistors limit the amount of current that can flow to/from the virtual ground.

In your first circuit, that is not a virtual ground (or virtual earth), it is the signal ground. Using a signal ground in this way aims to prevent any small waveforms on the power supplies affecting the output.