Short answer:
Excel and access are two very powerful, but different tools. Excel is a spreadsheet where mathematical calculations are easily accomplished, while access is a database program that enables data to be sorted and displayed in many different ways. While each program has the ability to do some of the things you want neither can do them all well. If you can only use one program I would suggest Excel. You can write scripts to have excel manage inventories and generate marketing reports. The ideal would be to use both and integrate the results. Good luck