Many consider Starwood points more valuable than airline miles.
If 20,000 Starwood points = 25,000 airline miles (except UA), and you value airline miles at 2 cents per mile, those *points/Mile equal $500.

With the value of airline miles (I'm referring to coach awards, not biz or first) may be considered less than 2 cents a mile (if you pay $250 for a ticket, rather than cashing in your miles, the cost is 1 cent per mile); many *wood Amex holders (like me) believe that your 20,000 Starwood points can be worth anywhere between 3 and 8 cents per point. The best value for Starwood point redemption is in Europe; where high hotel rates justify cashing in your points. If a room cost $300, and you cash in 10,000 points, that's 3 cents a point.

If you book a 5 night stay (pay for 4 nights with points, get 1 free) at a 10,000 point per night property, that 40,000 points. If you save $200 - $400 per night (times 5), that's a lot of $$$. Thats 2.5 cents to 5 cents per *wood point. Hence, the better value of the Starpoint.

Of course, your mileage may vary.