In a 1500pt list the Emperor is probably enough launch bays. I'd load up on escorts (5x Swords, 3x Cobras, 3x Cobras, if possible) and that leaves you with points for a mix of four standard cruisers. That's a fairly normal list and I'd say it doesn't make too big a difference which you pick.
If you like to combine bombers and torpedoes, remove Swords, use all your Cobras, and use a Mars alongside the Emperor.
I struggle with the Imperial Navy in 1,000pt games so I don't feel qualified to give advice at that level...