A camera, lens, and flash are the basic tools of the trade for a photographer. Just like a painter has a set of brushes and sculptor a set of chisels, a photographer needs to have the basic equipment to capture the scene. When I think of history's great artists, the one thing they all had in common was they knew how to use the tools of their trade.
There are types of photography where using the best gear is not necessary; wedding photography is not one of them. I use the top-of-the-line Canon cameras, lenses and flashes. Many professional photographers use comparable equipment from Nikon. Regardless of the manufacturer you prefer, I recommend investing in the best camera body and lenses you can afford—ideally, the top-of-the-line.
It is important to use the best camera body and the best lenses available for a variety of reasons. Let's start with the least obvious. When you pick up a great top-of-the-line professional camera and lens, you just feel better about everything. It's like when you put on a great suit or great pair of shoes. It gives you a feeling of confidence, makes you look more professional and gives you more credibility.
Using the best also ...