I was there last week with my 8 and 5 year olds. We went both US and IoA, and everyone liked both. To list out the "very best favorites" for the kids:
DS-8 --- MIB [did twice] (US), Jurassic Park ride (IoA), Camp Jurassic (IoA), Dooms (IoA), BTTF (US).
DD-5 --- Pteranodon [did three times] (IoA), ET (US), Camp Jurassic (IoA), Ghost Busters show [danced and sang along] (US).
I think you will have fun either one you choose. Ideally, you want to spend at least two days and do both, though.