You need design elements that are easy to rework into various formats. Photoshop can help you prepare your base image for maximum flexibility.
Illustrator makes it easy to implement all the artboard templates you deigned for your format needs (for example, a square for Instagram, rectangle for Twitter, various web banners – along with other templates for physical objects like stickers, t-shirts, mugs, etc.).
You now have a stunning ad campaign that’s perfectly designed for your client’s format and size requirements, and ready to launch for business!