As a cosmetic dentist in New York I use different types depending on the situation. Most often I use "hybrid composite". This is a category of composite that has been in usage for a long duration and has 'stood the test of time'. Hybrids have variable particle size for their 'fillers' and are usually considered the strongest type of composite when exposed to biting forces. They are less polished when compared to 'microfills'(smaller particle filler size) but most of the time the exact amount of polish is not the most important feature. Teeth are most often viewed in a 'wet' state and when viewed this way hybrids often are highly esthetic. If needed hybrid composites can be veneered with microfill composites, so that the restorations can appear shiny even when the restorations are viewed in a dry state.
A newer type of composite has been developed that is promising and has properties that mimic the best properties of hybrids and microfills. These composites,termed nanofils(Esthet-X is one example)are both resistant to flexing forces like hybrids and also can be highly polished like microfills. I have used these succesfully for anterior restorations but have not tried them for posterior restorations. Posterior fillings are under the greatest stress and I am currently using only hybrid composites for fillings in stress bearing areas on back teeth.
Currently Cosmetic Dentists must choose which of these types of composite to use in each situation. All work well when used in the correct situation and most cosmetic dentists have their own opinions on which composite to use for particular applications. There probably is not a universal composite that is best for every application.