Carl Sagan's Cosmos

Can anyone tell me what the difference is between the various Cosmos
DVD Sets there are out there? I've seen "The Complete Collection",
"The Collector's Edition", "The Full Screen Collector's Edition", and
the "Carl Sagan Edition" advertised but have no idea what the
difference is between them and don't know which one I should buy.
Help...I need my Carl Sagan fix...

Thanks very much for any and all help on this.

Best Regards,

Tim