I haven't noticed a lot of difference. We sometimes wait till afternoon to go to the park. The Disney park our son works at closes about 2 hours earlier than SW during the winter months and is about halfway home to UCF, so he meets us there after work for dinner.
The park is different than Disney parks after dark, especially when there is no fireworks planned. The lighting is minimal so it is almost like strolling down a quiet street with your family.