As someone who's been to both CP & IOA/BGT in the last 7 months, I would say go to IOA/BGT. I'll elaborate:
Supposing you've never been to either place IMO, CP has 5 really good coasters, Raptor, Mantis, Maggie, Millie and Gemini. Blue Streak is okay, Disaster Transport is quirky fun and WildCat is good for a cheap pop.
BGT/IOA on the other hand has 7 really good coasters Kumba, Montu, Gwazi (both sides) Fire, Ice and Hulk (though I dont think Hulk is *great* it is good).
So while CP has the *absolute* advantage in coaster count, I think the quality of the IOA/BGT combo is superior.
Also, as mentioned CP has nothing comparable to IOA's dark rides and water rides. And the Gwazis are great woodies (CP fails miserably in that department). You would also get to experience two totally immersive, jet differently executed theming patterns. IOA is an in your face juxtapositon of imagery. While BGT is a surreal look into a real environment. Oh and did I mention free beer? (hit your parents with that one ;))
lata,
jeremy
--who does note that there is something to be said about travelling 93MPH right off the ground...