Correct me if I'm wrong, but usually the first and last quarter are points based. Usually a 3x points type of deal. Around May you may see free night promotions, where after a certain amount of stays you will earn a free night. This may be a weekend night or a resort night.

My suggestion is that if you are thinking about switching over to Starwood, wait and do a platinum challenge if they announce a free night promo. Also, if you have an Amex Plat you can get gold status for free.

I haven't read much about the crossover program, but it looks like if you have gold status at least with Starwood you will earn SPG points on Delta purchases. You will get some of the benefits, but not the upgrades of a Platinum due to your status with Delta.