Your question is like asking which of the big three is the best TV. They are all good. Do a search with a large pot of coffee and you will be busy for hours. But I do highly recommend using TPMS on all tires. Mine has saved me two times from a tire failure on a busy freeway.
TST 507 system, very small monitor. External sensors with replaceable batteries on the truck rear tires. In-wheel sensors with supposedly 7 yr battery life on the rv tires. Cost was $370. I liked my old 510 system and I think this system will be even better.
There was a Trailer Life article in the August 2011 issue that listed nine different systems. I've been hanging on to the article, thinking it was a good reference for something I needed to get before our next long trip.