There is more to Belize than AC . .but, if it were my first trip . .I would head for the island.
...says the guy who never saw cayo! (kc - u know i love you!)
seriously, no one else took the other side, so i will (a bad habit).
i did the surf & turf my first trip, and loved it. i love cayo, and over the years returned twice more. but as stated, it isnt for everyone.
in my opinion, it is worth it if you have a few tours planned (xunantunich, rio frio, atm....and so forth). ps - while the jungle has a lot of insects, it does NOT (in my 3 trips) really have mosquitoes.
when i go, i plan it the same way - 3 nites jungle first, then 5 nights relaxing by the reef.
to each his own, just giving the other view. either way you decide, you will have a great trip!