The more plys a tire has, the stronger is it. So to increase your chance of a flat. You would want to go the minimum ply you could put on your car. With that said, just because the side wall is smaller, doesn't mean you're Chance of a flat is greater. It depends on the ply rating that tire has. Also depends on how fast you hit a pothole, how deep the pothole is. I have 10 ply tires on my truck, iv accidentally hit good sized potholes. Nothing happen. But I was also going maybe 30-40mph. If I was going 70mph, it probably would have done something, or nothing. Lots of variables to consider. Vehicle weight also plays a factor in that. My truck weighs 6800lbs. My car weighs 2500lbs. Way more force is on my truck tires then my car tires when you hit something. But my car tires are no where near as strong as my truck tires. Sorry for the long ass answer.