I have an old scar on my heel with a bony bit right underneath it that only acts up when I am wearing boots. Reviewing the leather boots was a serious challenge for me because a day of hiking resulted in a huge blister and soreness on that spot unless I pre-emptively padded it up and taped it up. Trail runners have NEVER bothered it.

Another example of how individual such things can be... there is no general rule of thumb.

Also, I have to wear men's sizes. When they measured me out as a women's 10 and I tried to use trail shoes that size, it was horrible. In a fit of frustration I tried on every shoe in the store until I found men's shoes in 10.5 did the trick, and haven't had a problem since. Women's shoes are too narrow and scrub the skin off the outside edges of my feet, right at the ball of the foot.