I noticed this thread has derailed a bit (but not in a bad way) from differences between the Lucifer and the Sathanas fleet to shivan agenda and tactics differences between FS1 and FS2.
But I would like to bring up an unmentioned aspect of the differences between the Lucifer and a Sathanas: Simply their looks and associated psychological effects.
In my opinion the Lucifer is very unique and menacing in design. The image of those two 'antennae' on it's bow, and those glowing spots on either side of it's 'head' giving an eerie feel of eyes, will NEVER leave me. The Lucifer, in my eyes, is the ultimate evil being; unstoppable, and immensely powerful.
The Sathanas, on the other hand, was boring, and uninspired in design. A big bulky body with four big spikes protruding from it. The Sathanas is portrayed as far more powerful than it looks, the Sathanas does not scare me. A cain scares me more. Also, the fact they had several dozen of them, while can be construed as a a kind of massive unstoppable fleet, comes off to me as making them mass-produced and expendable.
There's only one Lucifer, and it will always be more badass than the Sathanas in my opinion.