I have, been to the bahamas once and turks and caicos once as well. To be honest I liked both place's but turks was alot nicer, well keep island.
Out of the both I would recommend looking at the mayan riviera next to Cancun if you want a really nice beach experience. People were nicer here to locals and the water was alot nicer.. and theres alot more to do.
I have traveled to Costa Rica, Chile, Colubia, Baja, New Zealand and Fiji but i really love the Cancun area. Its not as small as the bahamas but not a large a Costa,Chile,...you dont have to travel 4 hours to go to the beach and 4 more hours to get to the forest... Everything is about 30 mins away..
Plus+ is alway cheaper/faster to travel down south from Cali then cross the whole nation - land in FL and take a connecter...
jMHO, hope this helps!