[Sammi]

Just closing well known ports will mean less drive-by sniffing. Which is an improvement. Doesn't mean you are now completely safe - it's just an improvement. At the very least it will make your logs smaller, as they won't be as full of drive-by sniffing.

Security is an onion, you can add layers. There is no perfect security. You can add hurdles and hope you make yourself too difficult for you adversary. Some hurdles add more than others, and not using well known ports is on the lesser end of the scale. You might still find it worthwhile, just so you have cleaner logs to sift through.