Well The QL17 is smaller then a G series Yashica. The canon has a 40mm 1.7 lens where the Yashica is a 45mm 1.7 lens, The canon works in a shutter speed priority mode in Auto ( you chose the shutter speed and the camera sets the app accordingly. The Yashica is app priority, you chose the app and the camera chooses a shutter speed between 1/30 & 1/500.
Both are very capable cameras. The QL17 give you full manual control but dose not meter in manual.
The Canon's Lens is slightly wider then the Yashica.
As for size here is a direct comp.
The Canon is a camera that you can carry in a pocket if you like. The Yashica, well you need a big pocket. As to performance I personally think they are about even. I have both and use both. The Canon is just an easier camera to take along sometimes. Each has it's own issues and things to look for when buying one.