It is a matter of personal preference. On one of my trips down to Costa Rica last year, I was waiting for my flight in the Houston airport and I saw a friend who I used to work with in the 1980's, but had not seen since. He lives in Phoenix but also has a house in Playa Portero, which is across the bay from Flamingo, and is as far as the paved road goes north from Tamarindo. He obviously prefers the quieter location of the Flamingo area.
My wife and I prefer the larger selection of restaurants, shops, and nightlife that are available in Tamarindo and the longer beaches of Tamarindo and Langosta. I have previously described my wife as a "foodie," and if you don't believe me, check out one of her restaurant reviews on her http://www.scottsdaledailyphoto.com/ website.
We also like to think that our two condos in Langosta and Tamarindo offer a nice contrast. Langosta is a quiet residential area, with a few restaurants very close and the rest a 10 minute walk to Tamarindo. Our condo in Tamarindo is near the beach and on the grounds of a beautiful resort, and it is right in the middle of town with dozens of restaurants within a couple of blocks.