Uuuppps,
it seemed that Reefrunner changed his management, so the situation to dive with them can be quite different,
and i hope that the difference is in a good way, so give them a try.
Watertemp ist not quite different between caraibe and pacific side in CR,
but consider that the big earthquake 1991 in the carribean sea lifted up the reefs and most of them died.
A scientific study about a marina project in Puerto Viejo from 2004 unveiled that 9% of the Corals are still alive and recovering slowly. Sadly corals recover VERY slowly...
Even if the caribbean sea is still the same, the costa ricean part of it is ways diferent of belize, mexico and the carribean islands.
The pacific is more turbid, has sometimes strong currents and surges and lost of plancton making the water greenish, butdue it "roughness" it has big fishes, sometimes very big ones.
Diving the pacific side of Costa Rica is the better choice and almost 90% of diveops are along the pacific shore, and this not without a reason.
Just travel around here in Costa Rica, dive by your self the spots and make your own decision, this would be the best way to discover Costa Rica.
Best regards
Chris Karrer