I agree, your not doing either country any justice in 5 days. You also dont say when your going, diving can vary greatly by season, and country, and coast?
Touristy, depends if you want to see and go on the regular circuit, or go where few go, which is 95% of the country. Avoid Monteverde, Manual Antonio, Jaco, Tamarindo and you just beat 75% of the crowds....
Best diving in CR is Drake Bay at Isla Cano, on the edge of the Corcovado park, the gem of the region, a remote place only 10% of tourist go to, but the highlight.
Best diving is Coco Islands, Liveboard only and 300KM off the pacific coast, all protected and Top 10 world diving, about $250 day and more than OW cert is needed, advanced a must.
I am sure Roatan is great, for good measure developers are builing on the outlying islands, as they are not protected. Hang out there as well and explore the Miskito coast, thats hot new destination BTW-