Yea, slower can be better, but not really harder. Spectators don't care if the trick is hard, they have no idea if it's hard or easy and they could card less. As long as the effect get's good reactions, I don't care if it's easy. I do prefer harder stuff, and sleights, but easy is fine too. As long as the spec enjoys the show, I'm good.
back to the effect: It's nothing ground breaking, and because of the cutting the deck, and too much excesive handling of the deck, the inversion wasn't surprising at all, and didn't really have a magical feel to it. Just trying to give you some helpful advice.
I think the Slower = Harder statement was meant for a perspective of the audience and not the method itself.
Most people believe that sleight of hand happens fast, however a slow pass can be down right devastating if there is no tension on the move. A fast classic pass is great but a lot of people telegraph it too much.
Dan and Dave are a perfect example here. The moves that they produce are very well practice and handled which makes them great. Work on handling and perfecting you effects before creating an effect. The effect overall was nothing amazing and can use some work.