rock face will not make it uncomfortable. bullnose is best way to go for ultimate comfort when sitting on the pool ledge

Hello, and thank you for your inquiry. As a general rule, it is an aesthetic choice. The rockface can be uncomfortable for bathers sitting on the ledge, exiting the pool, or leaning back against a spa wall. This will depend on the quality of the rockfacing, but it can have jagged edges from the process of facing it. With the other facings, it is a design decision. The bullnosing and fullnosing with the rounded edge looks more traditional, and a architectural squared edge or variant thereof can lend a cleaner, more modern look. The only safety concern will be the degree to which the edge overhangs the pool wall. Many municipalities will require a hand-hold, or minimum overhang onto which a bather can grab for safety. Many designers/builders will eliminate this hand-hold because a flush look will look cleaner in some applications. Be sure to check with your local governing body to ensure that you are meeting the safety codes. The other thing to consider is whether or not there will be an automatic cover installed. While undertrack systems have come a long way since they required bolting to the underside of a coping or deck, it is still nice to visually obscure the track system somewhat by overhanging the coping or cantilevering the deck.