In my opinion, when you're analysing a performance character, you have to consider their internal processes as opposed to their external expression. In other words, Penn's character may talk a lot, but talking a lot isn't his character, it's just something his character does. External expressions like costume, choice of vocabulary, demeanour, etc. may tell us something about the character but they don't define it. Do you see the distinction?
So, with that in mind, let's talk about Slydini. To me, he always comes across as playful. He's not trying to impose any profound meaning on what he's doing, maybe conscious that the beautiful sleight-of-hand carries the weight of its own mystery, and he has an almost childlike joy in the way objects vanish and appear at his fingertips. Even though he's clearly in control of what's happening, and every gesture is minutely choreographed, when magic happens he's still fascinated and enthralled by it. The character of Slydini is someone with a deep affection for magic for its own sake and who wants to share that affection with his audience. He doesn't want to show how amazing he is, but how amazing magic is, which is a crucial difference. Even when he says "I'm-a gonna fool you", the subtext is, "Come and play this wonderful game with me".
There's more to Slydini's character than that, of course. He's also someone trying to educate his audience about how magic should be experienced, but, to me, his childlike lack of cynicism is what makes his character engaging.
