True power players scurried between two events Wednesday: opening night of Bette Midler’s “I’ll Eat You Last,” about überagent Sue Mengers, and Barbra Streisand’s 71st birthday bash. Ironically, “Last” opens with Mengers having just been sacked by Streisand. Produced by a team including Vanity Fair’s Graydon Carter, the show and a Russian Tea Room after-party brought out the A-list, including Jon Hamm, Mayor Bloomberg, Barry Diller, Ali MacGraw and David Geffen. But a VIP said Babs’ bash, hosted by Donna Karan, later “hoovered up the crowd,” which headed to the West Village. A rep for both Streisand and Midler quipped: “Another amazing night on the big town.”