I think there needs also to be some separation between the idea of a safe pilot and a precise pilot. IFR training will make your more precise, and is a term that describes you ability to accurate and smoothly control the plane (granted hours will do this also). Do not confuse that term with safe. Extremely precise skilled pilots can still be unsafe if they make bad decisions. Being safe is much more of a mental game, and applying common sense. Also, becoming complacent can be a big issue. There is a reason that a pilot with around 250 hours is statistically the most dangerous. They have been doing it long enough that they become lazy and complacent because they are too comfortable and overconfident.
So from a gaining hours and practicing standpoint IFR training makes you safer, but nothing would stop you from improving from just going out there and flying with you PPL. Both potentially make you safer.
Remember what many people have said to me.
Your PPL is a license to learn.
Your IFR is a license to kill yourself.