They are completely different effects. The methods and routines aren't all that similar at all. Tornado is a transposition of 2 corners from 2 cards. You only use 2 cards. The sleight of hand is extremely easy to do, the gaffs do all the work.
With French Kiss there is preparation and some sleight of hand to be done. If I'm honest the sleight of hand for French Kiss is a bit more difficult. That's fine though because the transposition between 2 cards inside of someone's mouth is a great effect!
They are just different, they each have pros and cons. I've seen them both kill.
Answered at 11:03pm on December 5th, 2019 by joshburch (420 karma)