product or service - which is better business model

You need to be doubly sure about an product or a service that you are launching and for that you will have to be in the market place and take the pulse of the market. Read the competitors and the devise a game plane. This game plan has to have long term and short terms goals. It is these goals which will always keep you on track.
So learn these lessons well and you are on track for a good business to flourish and grow.
There are examples of businesses in the corporate where the busyness launched the products after reading the competitors weaknesses and strengths and that has simple provided them with enough arsenal to destroy the inventor.