Lucius is a bit cartoon-villian-y, which makes it way more fun but also less practical irl.
Lucian is very classy and posh, maybe too posh for some. Both names are really lovely. I'm hard pressed to say which one I prefer.... I feel like
Lucian is "safer" but gosh it's beautiful.
I guess, if I had to pick one to use, and also had to use my surname with it, I'd go with
Lucian, because my last name also starts with an L and ends with an "-us" sound, so
Lucius might not be the best choice there. Too rhymey.