Human:
Hmm. Any such variations with the SRF06 sensors?
It doesn't appear there's different types of SRF06 sensors. But, I wouldn't be surprised if there were multiple manufactures. Also, the SRF06 won't work using one pin unless you put a cap across the trigger and echo pins, and, even that doesn't work with the Teensy. The ability to use only one pin is a huge advantage as in many projects multiple sensors are used and pins can be in short supply. For that reason, I'd lean towards the SRF05, which for at least one manufacture is actually designed to be used with only one pin.
Tim