Ultimate Rewards points purchase program is stingy compared to American Express Membership Rewards:
Chase forces you to accumulate points gradually, gambling that the redemption will be good value when you need them. American Express allows you to buy enough for a trip after you have confirmed award seat availability, and American Express has many more transfer partners.
Not only that, but Amex allows you to "advance" points for free, assuming you earn them back (they charge you the going rate if you don't spend enough to earn them back).