New phone - New SIM or Old I am getting a new phone. I have an old Galaxy and am getting a new(er) one to use with my pre-paid plan ($30/mo unlimited).

I plan on keeping my old service and phone number. 

Should I use my old SIM card or use the new SIM that comes with the new phone?

I don't know if there are any reasons why I should keep my old one (like keeping data) or to use the new one (such as new features or security reasons).
If the new SIM uses the same phone number and plan, throw out the old SIM and use the new one. If it seems to change your number, keep the old one if it fits in the device.

The new one is indeed likely to be more secure.