I would sincerely suggest you to stick with the stock size, which in case of your ride, is none other than 195/65/R15.
In my Vitz, I up-sized from 165/70/R14 to 185/65/R15 (increase in width as well as rim size, and ground clearance), and deeply repented and regretted later.
Only plus point was Ground Clearance. Steering and Ride became hard, fuel efficiency dropped and I had to take extra care, otherwise, suspension ka bera garak ho jata.