How to Rend Fiends and Immolate People: A Guide to Sorcery

[Flashy]

Careful is a perfectly good option, but it doesn't affect the viability of your spell choices.

I quite agree with this. Twin is the sort of metamagic you choose your spells around, while I doubt there's anyone who has gone "Oh, I wasn't going to pick Fireball but now that my allies all automatically only take half damage I'm definitely going to choose it." It might be worth mentioning on unexpected stuff where the combo is exceptionally strong like Web or Stinking Cloud, but I don't think that every area spell in the guide needs to mention that you can make your allies auto-succeed on their saving throw and I don't think any spell should get a bonus to its rating based on how it combines with metamagic. That at most improves a spell from red to purple.