If you have not held personal AMEX cards historically, I would check cardmatch.com to see if you are eligible for 100k MR points on the platinum card before making a decision. B/t that and the PRG I generated 150k points in short order. It really comes down to what you value and your intended use of the points (premium int'l travel, hotels, lounge access, etc).

Starpoints are almost inarguably considered the most valuable points currency, but are harder to accrue based on limited sign-up bonues and bonus spend categories (unless of course you spend a considerable amount at Starwood properties). As a newbie myself, my focus is on AMEX, Chase, Citi, & AAdvantage miles for the time being...and I'm sure I'll add SPG sometime down the road