I reckon Amex is more considerate.
They may well be - Citi are pretty good when you ring up to "cancel" though I'm currently enjoying 1 bonus CitiReward point per $1 spent on my CBG (2.25pts/$1) until 31 Dec 2012 after I rang up to (legitimately) cancel it once I'd switched to Select. At least one other AFF member got an even better deal - two bonus CitiRewards points on their CBG (3.25pts/$1 total) until 31 Dec 2012 after an attempted cancellation.