Interesting article over at the Wages of Wins blog about the human tendency to choose potential over actual production/accomplishment. Considering what I've written about the Wizards offseason moves, I thought it worth addressing.
First off, the question itself is kinda off the mark. NBA teams aren't often choosing between an established "great" player and a potentially great player. The Spurs, for example, didn't get to choose between Tim Duncan and Anthony Davis this offseason.
Second, the question ignores the function of age and team situation. If the Wizards were abruptly presented with the option to acquire Duncan or Davis, they'd be foolish to choose Duncan despite the fact that he has a history of great play in the NBA. After all, Duncan is 36 years old and is in the final stages of his career. Davis is 19 years old, and while he might not be as productive this season as Duncan will be, the odds are that he'll be significantly more productive than Duncan over the next decade.
Third, this offseason, the Wizards weren't choosing between "great" and potentially great. The players they chose to add have warts. Okafor is a solid NBA center, but has a costly contract and is 30 years old. Like they did with Nene, the Wizards have purchased the wrong part of Okafor's career. Ariza is mediocre. Both have really been acquired with an eye to only the next couple seasons; neither is likely to improve much.
With the assets they had, Washington could have positioned itself to "get lucky" with a second rounder while still bringing in established players who are young enough to still present the realistic possibility of significant improvement.
In other words, Washington brought in proven players, but failed to improve the team's long-term outlook. They didn't choose "proven" over potential, they chose older, more expensive "proven" over younger, less expensive "proven" AND potential.