Mathammer - Smash Attacks

As someone who doesn't get to the table nearly as often as I'd like, I get some enjoyment from theory crafting around the hobby. In particular, I find mathhammer for certain scenarios to be interesting. After discussing a Flyrant's odds in combat with a Riptide, I thought about looking at when a Monstrous Creature should or should not smash.

In particular, I wanted to look at two of the more common MCs from other armies - Riptides and Wraithknights, and how the math worked out for each Tyranid MC.