Can any recommend to me which is better at the premium level?

I have Chessbase Light 2007 and like it a lot but obviously can't save anything which has proved troublesome as I have just found out recently.  I hear Aquarium is better for analysis but is harder to use.

Also while I'm here, what's the difference between purchasing Chessbase (which includes Fritz 11 I believe) and Fritz by itself?

They are really different products. Chessbase is a game database management tool, while Aquarium is an interface for a chess engine. A better comparison would be Chess Assistant vs Chessbase, or Fritz interface vs Aquarium. Chessbase unfortunately does not include Fritz, and to do automated game analysis you need the Fritz product or one of the other engine products that Chessbase sells.

Aquarium is a brand new product so it is going to have some growing pains, but they have some very interesting ideas for making a nice analysis environment for serious users. They also work really closely with the Rybka team. I will hopefully be getting Rybka w/ Aquarium over the holidays and can post more about it then.

You are able to interactively analyze games within chessbase using chess engines, and it has much more powerful database features than what is available in the Fritz interface. I don't know what kind of database capabilities Aquarium has, but I imagine it is more limited than Chess Assistant as well.

Thanks for the help.  I recently joined my local club (Scarborough Chess Club, one the bigger ones in Canada & Toronto) and the Chess Fed. of Canada so I'd figure I'd start to invest more serious effort into honing my skills but not sure the best route in terms of software.

I believe if you purchase a registration code for Chessbase Light 2007 it will allow you to save your games.  The old Chessbase Light 6 allowed you to save as well, but it probably can't load UCI engines.  The key feature in Chessbase/Chessbase Light is the automatically generated player, tournament and site indexes, and the ability to design your own custom opening, thematic and endgame keys.  In other programs, you usually have to run a search for a particular position or tournie rather than having them laid out for you automatically.

Aquarium is a database application with more features than SCID but less than ChessAssistant.  There is a lot of hype about Aquarium's Interactive Deep Analysis feature, but my first impression is that it is rather slow, and often misses critical moves that a human would try out if analysing.  Like Bookup/Chess Openings Wizard and ChessAssistant, Aquarium does have backsolving/minimaxing and batch EPD analysis, features that Chessbase lacks.  You can create opening trees for databases, but you have to do a search to find the games for each position.

Fritz is a playing program.  It can view but not edit the opening keys created in Chessbase, but not the player or tournament indexes.  It does have a friend mode to bring the engine closer to your level, and a coach will tell you if you make a bad move.  You can buy Rybka or Shredder with the Fritz interface from Chessbase.