The K12B is the regular 1.2-liter engine makes 83PS and 113Nm that comes with the V variant whereas, the K12C is the 1.2-liter Dual Jet Dual VVT engine with a mild-hybrid system that makes 90PS and 113Nm which is available in the G variant of Toyota Glanza. If you are looking for a more powerful engine with the better fuel efficiency of 23.87km/l, you can go with the G variant. On the other hand, if you want a more feature rich car, you can opt for the V variant. For more, follow the given link: https://www.zigwheels.com/news-features/news/toyota-glanza-launched-in-india-prices-start-at-rs-721-lakh/34062/#leadform
We appreciate your choice as the Baleno is an astonishing car.The Baleno Alpha gets a 1.2 litre BS IV compliant engine whereas the upcoming Toyota Glanza is expected to get BSVI engine options. Maruti has just launched Baleno with a new BSVI compliant Dura jet 1.2-litre petrol engine. If you are looking for a long term use car you can even check the Baleno with BSVI compliant engine. The BSIV engines will not be available on the cars after April 2020.
Toyota Glanza features MacPherson Strut suspension in the front and Torsion Beam at the rear. The ride quality of the Toyota Glanza is somewhat similar to the Maruti Baleno, which is better than other Maruti cars. Moreover, the suspension feels a bit stiff when hit the potholes but that stiffness gives better controlling on the highways.