I called to cancel Arrival+ ~3 weeks after AF fee posted. Because of the info in this thread, I did not inquire about any retention or downgrade offer.
However, the CSR passed me to a retention specialist, who offered me the no-AF Arrival card downgrade, keeping my credit line and existing points, and 1,000 points upon first purchase with the new card.
No AF, keep my account history and credit line, and bonus 1,000 points. No brainer.
Yes, it's a no-brainer that the offer is weak. I would cancel. You've only had the acct for 1 year, the history is worth very little for your credit score. The no-AF version of the card is useless and bonus pts are worth $10. You could cancel and reapply to get bonus again, or another Barclays offer.