I like RTR much more. It gives more units to build or hire, and gives more realism to battles. Big battles really feel big. It unites Rome into one faction, and starts when Pyrrhus controls Southern Italy. Also Britons and Dacia are removed. The map is expanded to the east, so Seleucids are as big as in reality and Bactria is included.
Very good, worth a try. Never played vanilla after that. Rome, Carthage, Macedon and Pontus are very fun to play, also Gauls are nice. It takes time to download it, but I recommend it.