I have a standard practice with CH's of contest that I win...The required formats are EPS and JPG...the reason being is that the jpg images are not true 300 dpi and are rgb and lower resolution...EPS is format specifically created for direct print and or placement into a document (it is not meant to be edited)
however I also supply
1. hi res jpg 300 dpi cmyk 2. hi res jpg 3000 dpi RGB 3. hi res Black and White 4. transparent background PNG 5 most important the Illustrator working file