well the 899 is the 'supermid' version of the 1199. The story goes that with the 899 Ducati wanted to offer the performance of the 1199 in a bike that was more refined for daily use. Using the 1199 for daily duty is like driving an F1 car to and from the office everyday. Cool sure but you start to miss creature comforts and start cursing the race tuned suspension and how they misbehave at low speeds.
the 1199 is a very well behaved bike, but like anything bred to go fast the 1199 is unhappy at low speed..
the 899 and 1199 use the same Superquadro engine in the 899 you get 898cc displacement, bore x stroke of 100 x 57.2mm and power figures of 148 hp/73 lb-ft of torque all in a package weighing 193 kg, very close to the magic 1:1 ratio.
Compare that with the 1199 where displacement is bumped to 1198cc and bore x stroke grows to 112 x 60.8 mm. Power figures or 195 hp/98.1 lb-ft of torque with a wet weight of 188 kg, beating the 1:1 power to weight ratio...
Both 1199 and 899 share Ducatis Quick Shift System. Basically power shifting for mototrcycles, up shifts at wide open throttle

as well as the same frame construction. They do have differing final drives as well.
Considering how similar the 899 and 1199 panigale are my biggest question is are we going to see an 899 Panigale S or Panigale R??