Capacitor Placements
Since in small signal analysis all DC sources are shorted, both circuits would result in the same small signal equivalent circuit. Connecting both capacitors to Vcc would also be equivalent. So for the signal it doesn't matter if the capacitances are connected to GND or the supply voltage.
It also doesn't really matter if the signal is balanced to half Vcc or not. There is no DC biasing done in those circuits. You might imply that there is some sort of voltage divider created by the capacitors which is not the case for DC.