Look at it like this Dominican Republic and Haiti or Costa Rica and Panama. If you decide on Costa Rica check out these three cities, Liberia on the Pacific coast, San Jose in the central part of the country, and Limon on the Carribean coast. CR is a very lovely country with beauty from top to bottom, also if you like a "green" place to call home CR is perfect. San Jose is a place that many say should be avoided, but I think San Jose has a charm about it that is hard to put into words. If outdoor activities is your thing, CR is second to none, hiking, biking, horse back riding, rain forest, volcanoes, beaches(playa Hermosa and playa Panama) are my two favorites.
I spend alot of time in CR, because I know a guy that has an apartment outside of San Jose and I use it from time to time when he is back in the states. Flights for me to fly to San Jose is alot cheaper then Santo Domingo, so at times I will go to CR for a 3 day weekend just to ride my bike. Everybody should have a place that they can call their own, and mine is San Jose, CR, not taking anything from Dominican Republic or Puerto Rico, but in this two places at times can be stressful.
I do not need to tell you about DR, because many other posters will tell you how great DR is. Which ever country you choose I hope you really enjoy the new life and culture of your new home, but you can't compare the two because they are just too different. Dominicans and Ticos have very little in common example, Ticos eat beans and rice ALL DAY long from sunrise to sunset, Dominicans drink far more then Ticos, and Ticos are more easygoing IMO then Dominicans. These are only my opinions you may form you own once you invest time in both places. GOOD LUCK which ever you choose
PURA VIDA!!!!