The way I see t Cryptic is using the Cruiser line as the basis for expanding the number and types of ships n the game. We seem to be seeing a blurring of the bounderies between the traditional roles..I suppose using the type with the most original trek type ships is a good idea for this
Excelsior is superior because of the Lt Cmdr Tactical slot which opens up so many possibilities. For instance you can carry beam overload 3 or attack pattern omega. It's the perfect assault cruiser and especially if you're a tac officer.