Ground Beef vs. Ground Pork
It won't. In meatballs, pork and beef will behave pretty much the same, the flavor will just be of pork or of beef. The only real difference that you're likely to see (other than flavor) is if you are substituting ground pork for beef of a lower fat content. Ground pork in the US is not generally labeled for fat content, but tends to run about 20% fat. Ground beef is common in that range too, but a lot of people choose lower fat ground beef as it is labeled for fat content.

If you want to find meatball perfection, check out Serious Eats.

Don't worry though, your meatballs will be fine.