205 60R 15 Tires

I've had my 76 280Z for 25 years. Other than headers, it's basically stock. When I got the car, it came with 195 50R 15 tires. With those tires the car pretty much steered itself on the highway and was good on curves at higher speed. On the negative side, the tires seemed way too small in the wheel wells, the speedometer was off by 10% and trying to turn it into a parking space took way too much arm strength so early on I got a set of 14 inch Panasports and 195 70R14 Pirelli P6000's. I'm happy with this setup but find, sometimes in a sharp turn, I get a little sway. The 205 60R 15 setup is almost identical in height, diameter etc to the 195 70R 14. I see from this forum that a number of people use the 205 60R15's and was looking for your advice. I'm not racing or doing anything performance based but I do enjoy a lot of New England 45 mph country roads. Am I apt to see noticeable benefits to the slightly wider tire and reduced sidewall? I still have the 15 inch wheels the car came with so the investment would only be in a set of tires and, of course, I could always go back to the 14's. Your thoughts would be appreciated. Thanks.

Dave