For pull-ups, some horizontal bars are a straight bar:
While others are bent at the ends:
When a person is in the upper position (using straight bar) their wrists will be straight, but in lower position their wrists will be tilted. Using a bent bar a person's wrists will always be tilted. The bent bar type is very popular but, on the other hand, I see that barbells use a straight bar.
Which is healthier? Which is better?