You can get a lot of info here [Link: remotecentral.com] and in the FAQ

The TS1000 was the first generation of Pronto's. And has been discontinued for over a year. The TSU-2000 is its replacement. They doubled its physical memory and added a IR database. It gives it about 2.5x more space for your configuration then the original remote (380 K- 960 k). The RU 940 is the European equvalent of the TSU-2000 but it does not have the IR database so it has a lot more space (1404K)