I like the union of the two. Lex Luthor's this guy with a brilliant mind but this thuggish mentality where he looks for every possible opportunity to expand his wealth and power. And when Superman is the obstacle standing in his way, well, mad science seems to be the route for him to go. Even when he is a businessman, he's playing the mad scientist field. It's just sometimes more efficient to slush Lexcorp funds into secret weapons projects rather than trying to perfect the technology by himself.
The ideal Lex Luthor is a ruthless and sociopathic businessman who's driven to mad science by Superman.