We've been to US/IOA three times. Every time was in late July, early Aug. We had nooooo problem getting both parks in. The most recent time we went with my DW's sis, her two kids (17 & 14) and still had no prob seeing both parks in two days even with having to deal with "newbies".
My wife is a HUGE SW fan (we went every year when they had one up here in OH). And she was disappointed in Orlando.
The park layout is horrendous. The rides (Kraken) was great but as for the rest of the park. I would not recommend it.
Never been to Discovery Cove. But my wife did do the dolphin experience in OH when they were preparing the animals to be sent to Orlando. THAT was neat.