Whats more effective - offering something for free in your CTA or benefit-oriented CTAs?

Calls to action are absolutely necessary if you want to engage with your audience and increase your conversions, and yet they should be written in such a way to appeal to a knowledgeable audience well versed with advertising & marketing techniques.

Personally I love a free trial, I will sign up for apps, programs and basically anything I am interested in (granted only if they dont ask for a credit card) and I can basically guarantee that if I am slightly interested in something I will sign up for a trial if the CTA is effective.

Another CTA that often works is a benefit-oriented CTA - something offering benefit to the customer. Something like Find out how to Lose 20kg and get fit for summer or even Find out how you can work 1 day a week and start living the life youve always dreamed of

Instant gratification CTAs are also another little winner in CTA land. With CTAs that are simple and direct such as Download now encouraging people to sign up and cut through the usual marketing hoops.

In your opinion, which is more effective or is it much of a muchness?

I know it would probably depend on what you are selling or offering, just curious what you'd ordinarily use when you're writing your CTA.