[kamocat]

I have found that using the measuring the digital pulse on the Maxbotix SONAR is much less noisy than the analog signal. (It also doesn't have the trouble with maximum slew rate).
Granted, this is with FRC hardware. The characteristics of your control system will be different. (You may have little enough noise on your 5v power supply, and a pulse-length-measurement that is not as accurate as an FPGA, and so analog may be a better choice.)

EDIT:
about those rangefinders: They have a MINIMUM distance around 5-10 inches. (it will say on the datasheet). If you get closer than that, you will get false readings.