Which address to send?

im going to sending my renewal app soon do i send it to U.S.Postal Service or USPS Express Mail/Courier heres the link https://www.uscis.gov/i-821d-addresses and whats the difference?

USPS = REGULAR USPS AND OR PRIORITY

USPS EXPRESS MAIL/COURIER = USPS EXPRESS (USUALLY 1 DAY, $20+ POSTAGE) OR COURIER (UPS, FEDEX, ETC).

Why the difference?
look at the address.... PO BOX VS Physical address.

I recommend Express Mail, it is faster and you can get signature confirmation.

Signature confirmation is must.