Thanks to Decious, more current (but still pre-Katrina) population figures are available for the OKC & NOLA metro areas, for what such comparisons may be worth.

The Census Bureau shows population estimates as of 7/1/05. The OKC SMSA was 1,225,084 and the NO SMSA was 1,319,367. I have no knowledge if more current Census Bureau figures exist (i.e., post-Katrina).

OKC: http://www.dougloudenback.com/hornets/okc7.05.htm
New Orleans: http://www.dougloudenback.com/hornets/nola7.05.htm

During the 5 year period, the detail reflects that the New Orleans metro gained 2,857 from 7/1/2000 ~ 7/1/2005, an 0.217% increase. The increase largely occured because St. Tammany Parish increased from 191,268 to 220,295 (15.176% increase) and less significant increases in Plaquemines, St. Charles, and St. John the Baptist parishes, offseting declines in Orleans parish (484,674 to 454,863, -6.151%), Jefferson parish (455,466 to 452,824, -0.580%), St. Bernard parish (67,229 to 65,229, -2.774%).

During the 5 year period, the detail reflects that the OKC metro gained 64,142 from 7/1/2000 ~ 7/1/2005, a 5.25% increase (1,160,942 to 1,225,084). The largest increases occurred in Oklahoma (660,543 to 684,543, a 3.5% increase) and Cleveland (208,016 to 224,898, a 11.15% increase) counties. No county in the metro lost population.

Graphically, the comparison looks like this: