I have a TST 507. Started with the nonflowthru sensors on our previous rig. They worked well, gave piece of mind, but were a pain to add air when necessary. Also I was concerned with the added stress on the valve stems.
When we got this rig, I had the tires replaced and had the shop install the internal sensors. Very happy with these, although I did have to install a booster (TST provided) in the trailer as they are just a bit too far away from the cab for a reliable signal.
Would not leave home without it.
2013 Jayco JayFlight 26RKS
2013 Ford F150 Ecoboost FX4
2003 Coleman Bayside / 2011 Jayco Jayfeather X20E -- RIP
2012 Tacoma Sport DCSB / 2013 Tundra SR5 - RIP