American Express upgrade offers often don't come to mind, and this is unfortunate for cardholders who are truly suited to capitalize on them. Currently, some Delta cardholders are being courted by spending offers that will upgrade them to a better card and give them a significant SkyMiles boost. However and here's the caveat these offers are only strategically sound if they're right for you, which is largely dependent on your card history.

What's available, who should think about it and who should give it a pass.

There are two upgrade offers currently available:

There are two upgrade options being provided for specific Delta business cardholders:

• New Delta Business Gold to Platinum: Earn 50,000 bonus SkyMiles in the first 6 months of their upgrade to Delta Business Platinum.
• In order to earn 60,000 SkyMiles, Delta Business Platinum customers must spend $12,000 within the first six months of upgrading to Delta Business Reserve.

The two offers will ask you to login to your American Express account and click on the "Upgrade Now" link. Those are actually targeted even if the links are spread around the web and if you don't see one listed on your screen, they're not available for you. There's no point trying to force access to an offer that isn't showing for your account.

The upgrade offers are valued at approximately 1.3 cents each Delta SkyMile, offering about 650 miles worth of Delta's SkyMiles for the 50,000-mile Gold-to-Platinum path and about 780 miles of Delta's SkyMiles for the Platinum-to-Reserve path. It's true value, but only in certain contexts.

The real system you're upgrading to

It's important to know what each card offers to understand if the upgrade is truly worth more than the bonus miles.

The Delta SkyMiles Platinum Business Amex has a $350 annual fee, and ups the ante significantly from its Gold level. Highlights such as a companion certificate for home or a trip to the Caribbean every year when renewing, $2,500 per year in Medallion Dollars to help with Delta elite status, and an annual $200 Delta Stays hotel credit, as well as priority boarding and two free checked bags, are just some of the additional benefits. The earning structure includes a 3X on hotel purchases and 1.5X on transit, U.S. shipping and large single purchases of $5,000 and above, making it more of a versatile business card that you can use day-to-day.

The Delta SkyMiles Reserve Business Amex, at $650 a year, is the cream of the crop in the Delta co-branded business card lineup. The most notable benefits of this level include the number of Delta Sky Club visits (15 per year or unlimited after $75,000 in annual spending on Delta cards), the number of Delta Lounge visits when flying Delta on the same day, the upgraded companion certificate offered in First, Comfort+ or Main Cabin, the annual hotel credit ($250) with Delta Stays, and the number of MQDs ($2,500), which doubles Delta's efficiency of earning status at the Platinum level (1 per $20 spent on Delta cards).

Critical Warning: Don't Do This If You've Never Had These Cards

One of the most crucial points in this entire article: If you have never had the Delta Business Platinum or Delta Business Reserve as your main cardholder, then you do not want to take advantage of these upgrade offers!

Here's why. Welcome bonuses are subject to American Express' lifetime once-per-card policy. Since this is an upgrade and not a new card, you won't get a card welcome offer when you upgrade. More importantly, by keeping the card over an upgrade, you will not be eligible for the welcome bonus of the upgraded card in the future even if you close the upgraded card and reapply.

Both of these upgrade offers are much lower than the welcome bonuses offered on the cards themselves. There are currently offers available to new applicants for 100,000 SkyMiles with the Delta Business Platinum, and 125,000 SkyMiles with the Delta Business Reserve. If you don't have these cards, it would be a high-dollar mistake to lock yourself into these welcome offers in return for a 50,000 or 60,000 mile upgrade bonus.

The following people may find these offers to be beneficial:

The upgrade is targeted at a specific, more limited set of users than they may seem to be. The following is a profile of cardholders who might want to consider doing one of these:

The most convenient way to get a good miles boost from a card change already qualified for the new card welcome offer: If you've already been a holder of the Delta Business Platinum or Reserve and taken advantage of the welcome offer, then the upgrade offer is the most accessible route to a decent boost in miles from a card change.

You have a Delta Business Gold or Platinum card that needs to be renewed and you don't have a retention offer: These cards could be worth more to you if you upgrade and get 50,000 or 60,000 bonus miles in the process than canceling your card outright especially if the increased features and perks are worth the extra fee.

The Reserve card's superior MQD earning rate (1 MQD per $10, compared to 1 MQD per $20 on the Platinum) makes sense for cardholders that are making substantial spend on their Delta card and trying to achieve or maintain Medallion elite status.

For all others, the new card welcome is much more alluring by itself.

Running the Spending Math

The spending amounts ($8,000 over six months for Gold-to-Platinum, $12,000 over six months for Platinum-to-Reserve) will be significant if you are interested in a strictly economic perspective.

You're spending about $1,333 a month at $8,000 over 6 months. If it's a business that is using the card for ongoing business expenses, that's fine. The calculation changes if a person would have to save or spend directly to reach that threshold.

At $12,000 over six months, the monthly average is $2,000. It's more serious, but still achievable for small businesses that have recurring vendor expenses, advertising bills or service charges on their credit cards. Those who already plan to focus their business spending on their Delta card for status will find the higher threshold much less of a hurdle.

The Bottom Line

Targeted upgrade members of the Delta Business Gold and Delta Business Platinum cards have 50,000 SkyMiles to earn by spending $8,000 to upgrade to Platinum from Gold and 60,000 SkyMiles to earn by spending $12,000 to upgrade to Reserve from Platinum. The bonuses are valued at about $650 and $780 each, respectively, at 1.3 cents per SkyMile. 

Here's the caveat: Cardholders who have never had the card they would like to switch to should forgo these offers altogether and opt for the new card welcome bonuses instead which are much bigger at 100,000 and 125,000 SkyMiles, respectively. These upgrades are best for cardholders who are not eligible for new card bonuses, are soon up for renewal of their existing cards, or are spending heavily with Delta and trying to get to Medallion status.