IMO I would go with the external duck antenna becuase you would have the option to mount the bluesmirf inside your chassis and simply drill a hole into the chassis and have the duck antenna be external from the chassis which would be a huge difference compared to having the internal antenna bluesmirf board inside the chassis.
I just bought the Bluetooth Modem - BlueSMiRF RP-SMA. I like the external “rubber duck” antenna for the same reasons mentioned. Probably a little better range. Also, it was the only one available when I ordered.
Mounting was simple, 1/4" hole in the PCB stock I used for the bracket, and a lock washer borrowed from a small toggle switch.