Now the longer part: Generally Cthulhu addon is more demanding, because you, there are many conditions and long texts on the cards, as well as tons of talent, pull each train in the length. That is why I would add-on actually reluctant to play second, because it takes so just a lot more time to complete and can be tough as chewing gum until a base is sometimes full or a real change occurs: Take madness cards, leg from insanity cards , get it from the discard pile, search your deck, including leg, then shuffle, etc. etc. a little time "on your tongue" like dinosaurs or bears riders remains off.
On the other hand there are some really brutal and long combinations that generate the greater sense of achievement. My tip: Play Cthulhu prefer for themselves, and worried you a second set to play three or four. The factions have quite their charm, so Miscatonic is easy going mad and the Fishman Innsmouth look like a cross between zombies and robots. The minions of Cthulhu are slightly insane and the alien beings are similarly strange how the spirits.
Finally, it should be mentioned that the translation notice nowhere TOO uncomfortable. But some cards have been translated really bumpy and it takes several attempts to tighten to what is meant. And what the heck do you mean "the final Cthulhu" ?!