Maybe this is a "duh" post, but maybe it'll allow someone out there to make the choice for themselves. Anyway, if you subscribe on the Bethesda launcher, know that Bethesda will auto-renew your subscription regardless of their previous messaging that they wouldn't be auto-renewing subscriptions that expire in April. The original FAQ page is still up and says: "In April, your Fallout 1st membership will not automatically renew. Once your membership expires you will need to renew your membership on the Steam platform. You can check the expiration date of your Bethesda.net Fallout 1st membership in your account on Bethesda.net."
The updated FAQ states: "On April 27, we will disable real-money transactions in the PC Bethesda Launcher version of the game, which includes purchasing Atoms and renewing Fallout 1st memberships. However, you can continue to spend any Atoms that already exist in your account until we disable logins in May. As mentioned previously, any Atoms that remain in your account after migration will be transferred to your linked Steam account."
Previous messaging indicates that FO1st benefits will transfer over to Steam (assuming this means tent & custom worlds) and that remaining atoms from the subscription will be added to the account. The updated FAQ doesn't mention anything specific about FO1st benefits. Hopefully that remains the case, otherwise some people may end up having to subscribe on Steam after paying for a year of FO1st on the Bethesda launcher.
Didn't see any mention of this specific change in the migration FAQ here, any gaming outlets, or by other content creators. Only posting this here so that you can decide for yourself whether you want to roll the dice with your FO1st benefits and so that you don't get hit with a potentially unexpected $100 charge (like I did yesterday morning). Especially due to the flip-flop on the originally posted migration FAQ and lack of clarity on benefits covered by the updated FAQ published on the 13th.
Bethesda must have decided that they needed that extra month of auto-renewals before starting to give Valve their cut. I guess billion dollar companies are gonna do what billion dollar companies do.