Jag har läst både bra och dåligt om dem båda. Här är ett omdömme från en som provat dem båda.
Actually, I bought both HST and Learn-Thai-Podcast (first HST, then LTP). I try to progress in both. Overall I would say I prefer LTP, I like the iTunes based video method, I like the How to Read and grammar videos. After doing a series of LTP videos, I go back to HST to read the equivalent lessons to consolidate. Customer Service at LTP is also quite good, although maybe not as responsive as Vincent. One issue with LTP is that the access to the website is limited to 1 year, but its not a big problem as you can from the very first day download all videos from beginner to advanced.
But as I advance more, I will need Skype based one to one lessons to correct pronunciation and develop conversation. Because the problem with both HSP and LTP is that no one will correct your pronunciation mistakes.
Mer finns att läsa om HST på http://www.thaivisa.com/forum/topic/462780-highspeed-thai-great-language-course-or-what/