The Tax Analysts' CD-ROM Worldwide Tax Treaties is invaluable when working exclusively outside the U.S., as it contains an amazing amount of material worldwide. Tax Analysts recently came out with a U.S. Tax Treaties Disc that contains the U.S. portion of the material on the Worldwide disc. Both products are scrambling to provide more material and to catch up with each other. The most significant difference is that the Tax Analysts' discs don't contain editorial material that can be used to provide links between various treaties. Another interesting difference is that TreatyDisk shows changes on the current version of the treaty.
Tax Analysts shows changes on the original version of the treaty.
I find the TreatyDisk approach more useful in figuring out the meaning of the current treaty for planning purposes. On the other hand, Tax Analysts' version of Help is more personalized, making it easier to use. Currently, TreatyDisk is missing the text of Friendship, Commerce and Navigation Agreements and the commentaries to the OECD Model Treaties. However, these are promised for a future release. Currently, only Tax Court and Supreme Court opinions are included.