Paul,
It really depends on what you want in a snake.
Carpets, as a group, tend to be nippy out of the egg, but typically settle down nicely within a few months. They are generally much more forgiving of mild husbandry fluctuations, and are fairly tolerant of temperature changes. Ball pythons, on the other hand, typically start out withdrawing from human interaction...though some do bite. Both can develop feeding responses, and both can respond differently to different people/situations. By the same token, both can (and usually do) adapt well to handling and make very good pets.
You mentioned that the snake would be something of a "display animal"...you might want to also consider the habits of the animal and the style of cage you would like to see in that area. I have both carpets and BPs, and the choice is an obvious one for me...but it isn't my front room that it would be decorating, lol.
(My apologies for not responding sooner - I remember seeing your first post, and planned on coming back to it...but, apparently, it slipped my mind. I don't recall getting the notifications of the other posts, though
)