Resume writing: What are the major differences between CVs and resumes? What should I go for and why?

You need to be clear in what is that your targeting and based on that you can showcase your profile. 

Understand that if you are sharing a profile on the social media Resume hold good, since its a synopsis of your achievements.

If you are targeting a particular job through a job portal, then its a targeted approach, where you need to provide all the details that would contain in the job description, by doing that your doors of the interview are opened. Name provided for this profile is CV.

Hope you understood the difference.