I have recently created a business card and when our company logo was incorporated the letters of the logo look flat.
The business card is standard size with the the original imported logo image being 6000x4200 png file. I tried making the size smaller by dragging the corner point to a smaller dimension but the result is flattened image that loses crispness.
Should I be using the png file or would it be best to work with the original .ai vectored file?
It's hard to understand what you mean by "flat" seeing as logos are, in essence, actually flat. Do you mean that you are working on a logo that should have a 3d effect or a hint of depth and resizing messes it up? Good logos should be scalable and would not get distorted no matter what size you make them.