For the 2020 Medallion Year (status earned in 2019), you receive one Platinum Choice Benefit (CB) upon reaching Platinum Medallion, and in addition three Diamond CBs upon reaching Diamond Medallion. You may choose these benefits individually at any time during the Medallion Year, so you might choose one Diamond benefit (such as Sky Club membership) immediately and wait to choose your Platinum benefit and other Diamond benefits until you need them.
All benefits must be selected by the end of the Medallion Year (Jan 31, 2021 for the 2020 Medallion Year)
Platinum Choice Benefits
4 Regional Upgrade Certificates (RUCs)
20,000 bonus redeemable miles (RDMs)
$200 travel voucher
$200 Tiffany gift card
gift Silver Medallion status to another person
Diamond Choice Benefits
4 Global Upgrade Certificates (GUCs) *OR* 8 RUCs *OR* 2 GUCs + 4 RUCs (upgrade certificates may only be chosen once)
Sky Club individual membership
Sky Club executive membership (allows 2 guests in addition to the member) as an upgrade from individual membership (this can be combined with an individual membership selection by using 2 Diamond CBs)
Sky Club guest pass (allows 2 guests in addition to the cardholder if you have access via Delta Reserve or non-Skymiles Amex Platinum credit cards)
25,000 RDMs
$200 Delta travel voucher
$200 Tiffany gift card
gift Gold Medallion status to another person
Expiration Dates, Other Considerations, and Related FlyerTalk Threads
Roughly speaking, there are three classes of Choice Benefit:
Choose as early as possible:
These will end at the same time no matter when you choose them, so you're best off choosing them immediately (or for gifted status, Feb 1 if the recipient had that status or higher for the preceding Medallion Year).
gifted status
Sky Club membership
Sky Club guest passes
Global/Regional Upgrade Certificates starting with the 2022 Medallion year
Choose as late as possible:upgrade certificates (GUCs and/or RUCs), Delta vouchers. These expire 1 year after selection, so if you choose them in June they will expire much earlier than if you choose them in December (or the January ending that Medallion Year).
Choose whenever (keeping in mind the Jan 31 deadline for choices): redeemable miles, Tiffany gift cards. These do not expire (AFAICT in the case of the Tiffany cards).
Regional and Global Upgrade Certificates
Expire one year after selection, so ideally you should wait until you want to apply one before you make this selection (but note the overriding deadline for selecting all CBs as noted above)
Starting with the 2022 Medallion Year, Upgrade Certificates expire at the end of the associated Medallion year. The example from DL's web site is:
For example, if you reach Diamond Medallion Status on August 1, 2022, then you will be eligible to select Choice Benefits for your 2023 Status and any Upgrade Certificates selected for your 2023 Status will be valid until January 31, 2024, regardless of the date they were selected.
Usually appear in your account within a few hours after selection. Agents may not be able to see them right away, but as long as you can see them in "My Wallet" you can give an agent the 006 certificate number and the redemption code via phone/Twitter.
Sky Club options expire at the end of the Medallion Year (Jan 31, 2021 for the 2020 Medallion Year) no matter when the selection is made
if you have Choice Benefit selections pending from multiple Medallion Years, be careful which year you are selecting from as this will affect the expiration date. The DL web site will list the expiration date of the benefit before you finalize your selection, so pay close attention. If you have multiple years in play, select from the latest year for the longest validity period.
there is a minor technical distinction in guests permitted between an Exec Membership (two guests, or spouse and children under 21 without any limiting language) and the Guest Pass (two guests) but in practice SC agents seem to permit spouse+children (even if more than two guests) for the Guest Pass as well.
certain Delta-branded American Express cards allow "Pay With Miles" at 1c/RDM; tickets bought that way will earn full MQMs, but earn MQDs based only on the dollar amount paid (if any). Since RDMs do not expire, this may be preferable to the voucher.
Travel Vouchers
Expire one year from issue, so ideally you should wait until you want to apply one before you make this selection (but note the overriding deadline for selecting all CBs as noted above)
travel vouchers used on future tickets will earn Medallion Qualification Dollars
certain Delta-branded American Express cards allow "Pay With Miles" at 1c/RDM; tickets bought that way will earn full MQMs, but earn MQDs based only on the dollar amount paid (if any). Since RDMs do not expire, this may be preferable to the voucher.
Gifting Status
gifted status expires at the end of the Medallion Year (Jan 31, 2021 for the 2020 Medallion Year) no matter when the selection is made. If you know this will be one of your selections, then select it immediately so it is effective as long as possible.
if you have Choice Benefit selections pending from multiple Medallion Years, be careful which year you are selecting from as this will affect the expiration date. The DL web site will list the expiration date of the benefit before you finalize your selection, so pay close attention. If you have multiple years in play, select from the latest year for the longest validity period.
status cannot be gifted if the recipient currently has that level or higher status
Tiffany Gift Cards
Tiffany gift card has no expiration date listed in the terms