Well both the USB and Bluetooth all convert to Serial I/O which goes to the UART on the chip. The "easiest" way to talk to the Arduino is directly via a serial port, which requires nothing more than the standard system serial driver.
Many clone Arduinos save complexity and cost by supporting only Serial (RS232), just run through a MAX232 chip or similar. My Adafruit Boarduino is of this type-- I use a serial cable to my MAX232 based Serial-to-TTL cable, which connects directly to the port pins (rx/tx) on the BoArduino. That way, the BoArduino doesn't need to keep that circuitry on-board, reducing size and cost.
My (and your) "standard" arduino uses a chip on the board to convert from USB to Serial, which is then connected the same way, through a max232 (look on the board) serial-to-ttl converter.
SO... Serial the answer. How you GET to serial; that's the question..
I've not used any of the wireless solutions (yet), but as I understand XBEE as well as most Bluetooth adapters simply act as a virtual wire.. the computer and Arduino talk over a serial link via bluetooth, the only driver you will need is for your own bluetooth dongle or builtin on your computer. Once paired, neither the computer nor the Arduino know or care that the connection is wireless. I have an older inkjet printer that uses bluetooth as a connection option.. once paired to the computer, it's just another COM: port printer. The actual drivers to make that printer work are another issue, but the connection is simple.
Range for bluetooth is supposed to be something like 10m, I find around 20 feet more realistic for most applications in a noisy electrical environment when using other bluetooth-connected items.