JOIN queries vs multiple queries

Are JOIN queries faster than several queries? (You run your main query, and then you run many other SELECTs based on the results from your main query) I'm asking because JOINing them would complicate A LOT the design of my application If they are faster, can anyone approximate very roughly by how much? If it's 1.5x I don't care, but if it's 10x I guess I do.