I say go fly the 747-400 for SIA Cargo. I hear the CEO of Qatari is a big, fat jacka$$.... You'll never fly a 400 at Qatari and you would likely never get to fly the A380 if it ever arrives. See the world with SIA Cargo instead - just don't expect it to be a great outfit from what I hear (keep your expectations low and you will be happy)... Let us know which you pick.