Use the old SIM card or the SIM in the replacement phone?

[CaDroidUser]

I have a Galaxy S4 which seems to be going down hill. I bought a refurbished replacement Verizon S4 online. Should I swap the SIM out of the old phone into the replacement, or use the SIM card that came in the replacement phone?

Thanks in advance.

 

[psionandy]

Which Bill do you want to pay?

 

[CaDroidUser]

The replacement phone is unlocked, but VZ compatible. I want the replacement phone to replace the dying phone. It sounds like using the old SIM card might be simpler. Are there any risks to that?