Every year we have gotten good value from the $99 (formerly $49) companion ticket, well worth the $75 annual fee.

Without that perk I am not sure I would keep this card - though with fares rising I will probably try to start cashing in miles for our annual trips to Mexico.

If you are looking purely at miles, it really is an individual decision based on your intended use of miles. BA and SPG both provide a better return (1.25 miles per $1) but you'd have to fly BA or one of the carriers that accepts SPG transfers.