The optimal texture format on all systems, regardless of endianness or operating system, is an internal format of GL_RGBA8, a type of GL_UNSIGNED_INT_8_8_8_8_REV, and a format of GL_BGRA. An optimal call to glTexImage2D would thus be this:
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, border, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, NULL);
Remember that because this is a packed integer format, you are responsible for taking endianness into account when packing the pixels.
GL_NV_pixel_data_range (look at NVIDIA Implementation Details).
Mac OpenGL mailing list