I found the "JB Luthor" to be be more plausible than the 'Superman must die because he made me bald!' version.

As for the 'purple jumpsuit', I believe somewhere in that 'Classic Covers' thread a week or so back, someone posted an image of the first appearance of that garb, a mid-70s issue (not sure if it was ACTION or SUPERMAN, though I suspect it was a Cary Bates story, and the two titles were almost interchangeable when Bates wrote both of them!) I think the caption referred to it as 'Luthor's Power Suit'...perhaps Bates ripped off, er, paid homage to, the armor of Dr. Doom?

"I found the "JB Luthor" to be be more plausible than the 'Superman must die because he made me bald!' version."

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Speaking for myself as a Bald-American: Someone's gonna pay...someone's gonna pay...

Lex Luthor is one of my favorite villains, in both pre and post-Crisis versions.

Pre-Crisis: Lex is a great genius, but he is the typical person who, when the morning begins, says "Today will be a great day!"... and then, a problem ruins it all. So, 'cause his baldness, he becomes a villain. I remember a sad scene in "The Luthor nobody knows!" where his father sent him away from their house 'cause his firts criminal action...
Lex wants to be better than Superman, and for this he uses his brain. But Superman is smart and strong, too, so Lex must be stronger. The introducsion of the purple suit in the mid '70s was a way to make him able to compete with his rival on the strenght field, and the Lexorian armor was another and better way. AC #544 (first appearance of the armor) is important for another reason: the deaths of Ardora, Lex Jr. and the whole Lexor planet. If before tha Superman/Luthor war was caused by an accident, now Luthor hates Superman more than before, because accuses him of having stolen him his new wonderful life (actually, it was all Luthor's fault).
A great character, tragic and powerful.

Post-Crisis: Lex is pure evil. JB's version of the character is dangerous and deadly, probably the most dangerous villain in that period. He doesn't need to be in the battlefield... He rules the battlefield. He is always guilty, but nobody knows the truth.
It's a pity that, after Byrne's departure, the following authors haven't used him very well. In my opinion, the whole fake death/Lex II/deal with Neron thing was very, very bad... It was an exageration, too complicated and a bit unuseful. I prefer the stories where he becomes President. That was the moment of his supreme triumph... I loved SUPERMAN/BATMAN 1/6, where at last Superman can put down him! Luthor's greatest plan... followed by Luthor's greatest defeat.
Oh, and I'll continue to tell it... Lex is not only evil. He is a madman. Do you remember the Pocket Universe? His counterpart was a nice guy, but he was a fool. He could stop the Kryptonians but preferred to fight... And caused the death of billions of men.

These two scenes sum up the reason for the pre-crisis Luthor's hatred for Superboy/man, but as much silver-age fun as those tales were, I think JB's take with Luthor as being jealous of Superman's abilities and popularity really makes a better story.

I like the post Crisis version. The pre Crisis one was quite a stretch to buy as an antagonist and all the costume and the hate theme made no sense to me.

JB's and Wolfman's version was a solid character, completely evil and menacing that we could find in the real world. I don't agree with the Kingpin comparison. The only thing in common are the lack of hair and the wealth. I imagine Luthor was far richer than Fisk, though, and he was not a super villain, as Kingpin. Not even a crime lord in the same sense. Luthor was a wicked person, but mostly a legal businessman and not the leader of the underworld. Kingpin would never bother to do what Luthor did in the "Metropolis 900 miles" story, which for me is the one that made Luthor a tangible character.