The x0xb0x power supply is a lot stiffer then the TB-303. The TB-303 can also run off of batteries, and disconnects the 6V power supply when the headphone jack is not in use. The stiffness of x0xb0x power supply does actually affect the ability to accurately reproduce the TB-303, because sometimes the TB-303's supply would be loaded down, introducing a resonance warble. These two issues are dealt with in the PsMods section.
The only difference between the x0xb0x and the TB-303 synth is the use of the 2sa733p transistors in the x0xb0x and the 2sa733ap transistors in the TB-303. See HighGainTransistors for more information.
Some TB-303s have a different NPN transistors in the transistor ladder VoltageControlledFilter.