Uploads are painful on satellite and the 2 second delay can wreak havoc with many programs.ISDN is barely faster than dial-up and as expensive as DSL and cable. I don't know why anyone would want it.
I couldn't imagine satellite being slower, except for games and stuff like that (being on satellite, it will obviously have a lag). But for straight browsing the delay in upload shouldn't matter.
The ISDN is actually faster than almost all satellite internet. It depends on what bandwidth you get.
I get about 128K downloads on my ISDN, on my Satellite I was lucky to hit 45K.