Re: For those who completed the story mode in GTA V...(Spoilers)
The method I used to watch all 3 endings without having to play through the story 3 times in a row was to save the game before doing the mission on 3 separate files. I saved one file for Option A, one for B and one for C.
Yes, option A & B do end with either Trevor or Michael dying. It occurs in the most anti-climatic fashion, too. They're definitely not the correct options to end with, seeing as the game just ends after they're killed without any closure on all the agencies/big names involved, such as Devin (the billionaire you steal those 5 supercars for) or Steve Haynes (the FIB agent).
Option C is the best for obvious reasons. Not only do all 3 characters survive, but every asshole encountered along the way gets killed, including Stretch, who was that ex-con former friend of Franklin and Lamar's. He was relevant for two story missions (and so far apart from each other that I forgot who Stretch was at first), and then became completely irrelevant, but R* still decided to add him into the death pool.