As usual it always depends on the situation and context. Qin's IND synergizes well with the Pavilion for cultural victories, while the Hippodrome has no particular synergy with IMP/SPI and kataphraktoi. Also, personally by the time I get Drama I'd either have gotten Monarchy, Mids, lots of luxury resources, or otherwise dealt with happiness bottlenecks. Hippo's extra happiness can play a role in very late game cultural victories when running Caste System over Emancipation, but Pavilion helps you obtain the victory faster. Hippo also does not let you run 2 artists like theatres can, so if for some reason you are on Eman and you need to run artists, Hippo cannot help you with that.