Both are acceptable tools that can both perform the task at hand, so in that sense it is a matter of personal preference which you prefer to use.
If you are anything like me, you don't have enough time to write a custom program for my own personal use to do something specific, so I would personally try to use Excel.
I can see both sides of the coin though, maybe your motivation to write a custom program is to learn new skills in Haskell or whatever the current fad is in computer languages today. I would see the learning exercise in this case as the real product of my efforts and the final application itself sort of as a bonus.
I wouldn't be so quick to knock on Excel either, certainly it is limited from a computer programming perspective but that is because it is purpose built and designed to be. I view Excel like a highly sophisticated calculator. I have worked with people who have taught me some AMAZING things that Excel is capable of, complex mathematical calculations, statistics, and deep analytical reporting that supplements data warehouse dumps perfectly. Experts at Excel can make a good living doing just that, so learning new skills in Excel can certainly benefit your career in some way shape or form.