Roger,
They are chalk & cheese. The first ones are very small (38mm high, biggest diameter 38mm) and you have to use the sleeve-type abrasives which limits your options on grits etc. This set can be found in a lot of cheap tool shops - I got mine for around €6(£4). Worth having for that sort of price though.
The second set are much bigger (3" high, biggest diameter 3") which makes them much more useful - I used my cheap set on that chair I posted, and I had to make two passes to sand at two different heights as the usable portion of the drum wasn't tall enough for my 40mm thick timber. They are also MUCH better quality and you can use any abrasives you like.
Neil