Definitely 75K MR points IMO. The 30K SPG offer seems to be recurring, and while it's likely you could be targeted again for the 75K down the road, I'd jump on it now. 75K MR points have a lot of flexibility. I got that offer two years ago, and moved them to BA during a transfer bonus promo. Came out with 100K BA miles and change, so 4 round trip tickets to Hawaii (I'm LAX based). My 75K MR got over $2k value to me with that...