I am a big .22-250 fan, but as much as I wish I could call it the king, it gets whooped by the .223 WSSM in the velocity department by over 100 fps.
I wouldn't believe everything that's listed on a box for velocity.. more than one ammo maker tends to exaggerate their velocity numbers from what I've seen. The .204 is great, but definitely not outrunning a .22-250 unless you have an extremely light bullet. 32-40 grain .204 loads, while fast, aren't going to outrun a 250 that's loaded with a 35-40 grain bullet.