Okay...the lowest one, the Power Pass, I believe it's called, will not get you discounts anywhere, the hotels, restaurants, stores, anywhere.
The next one up, the Preferred Pass, will get you discounts on hotels, restaurants, stores ... a few extra perks, too, like not having to pay parking at the garage (this does not extend to the hotels), a deal on valet parking, discounts on tix for folks traveling with you, etc.
The highest one, the Premiere, *I believe* has all the perks of the Preferred Pass (discounts), plus FOTL access after a certain time in the parks, some bottled water -- I'm sure there's a bit more, but I'm not remembering it.
So, anyway, if you just want the discounts but don't have a need for FOTL all year in the evening hours, don't need bottled water, I'd say to go with the middle one, the Preferred. It pays for itself very, very quickly.