Houdini-
Super innovative layout, challenging, it’s a long term keeper. IMDN is also awesome, you can’t go wrong with it either - my sense is there will be a lot of Maidens available on the used market eventually, just because of the volume of Sterns made. Time will tell how IMDN lasts, I am not sure. It sure is fun, but so is Houdini, and Houdini forces you to become a better player, which IMO is very rewarding