the 50 points are (if you finally exchange them into miles of your preferred airline) a little bit better than the direct 50 miles you get from your airline, because if you transfer 20'000 Starwood-points you get the 5'000 bonus to make it 25'000 airline-miles.

But for me and AVIS it will be LH's miles&more program for short rental-periods, still giving 500 miles per rental / no flight needed, worldwide.