According otomotif.com, Valentino Rossi said that there are 4 reasons why this Italian rider choose Ducati for next season.
The first one is internal changes on Ducati. Rossi said that this modern Ducati is very different with Ducati in the past year. Ducati is more dynamic. There's a lot of talk when Rossi sign contract with Ducati. The second reason is Masao Furusawa, first man of Yamaha. This is the last year for Furusawa in Yamaha. This situation make Rossi think, what will happened next on Yamaha without Furusawa. 7 years with Yamaha, for Rossi, Furusawa had a big influences to the team. It makes Rossi worry.
Third reason for Rossi is his mission for M1. YZR-M1 now being a great motorcycle. And all rider must count of it. It's about Rossi that makes M1 be like this. The last reason is about Rossi's personal thought. He like challenges and something new. So his reason move to Ducati is a correct decision!