The choice between First Class and Standard Mail basically comes down to how quickly you want your message to get to your audience and what you want to happen if some of your addresses aren’t right.
First Class Mail
First Class mail is processed by the USPS right away. Your postcards or letters will typically be delivered in 1-2 days locally, and nationwide in 4 days or less.
If some of your addresses are bad (i.e., your party has moved) your mail will be forwarded at no charge for a period of 1 year. If some of them are undeliverable, they will be returned to you at no charge, each accompanied by the reason for non-delivery.
Pricing is by the ounce, with a flat amount for the first ounce, a lesser amount for the next ounce, and so forth.
For bulk single piece First Class Mail (200+ pieces), the USPS now offers a small discount per piece. For pre-sorted first class mailings, the discounts can be much more significant, depending on the sort process used.
Standard Mail is processed by the USPS when they can get to it. As such, there is no guaranteed delivery time. Your mail will typically be delivered in under 7 business days locally, but nationwide it could take weeks. Standard mail is, in our opinion, a crap-shoot. You really never know how long it will take. For some mailings that’s just fine. You just want it to get there for cheap.
If some of your addresses are bad, you’ll never know it with Standard Mail. Standard mail is not forwarded, nor are any pieces returned to you if they are undeliverable. These items find their way in to the USPS “circular file”.
A Standard Mail piece can be up to 3.3 ounces before additional postage is due. And, depending on the sort method used, presorted Standard Mail can be considerably cheaper than First Class Mail.
Which one should I choose?
If your mailing is time sensitive, choose First Class. Period. If it is not, and you can deal with the uncertainty, Standard Mail may be the better choice due to the cost savings.