For some reason, i like to get Nar Shaddaa done first.
i think it's because it takes up the most time for me to complete, so it still feels like a linear part of the game like Peragus, Citadel Station, and Telos are. After that though, i approach it randomly, though M4-78 just seems like the other half of completing Korriban, since Korriban is a much shorter stop, and you're still in the process of locating Master Vash.