I agree with pretty much what everyone else is saying. You really should try to do both. You'll want to see what platforms your audience uses most and uses to engage with your content. You can't really find that until you try them out.
For example, one of my Facebook Pages has nearly 1M Likes. I tried cross-promoting a Pinterest for that same audience and they didn't bite. No one really engaged with the content on Pinterest or followed my account. So, I gave up on Pinterest and continue to focus on my Page while testing other platforms like Tumblr and Twitter
For example, one of my Facebook Pages has nearly 1M Likes. I tried cross-promoting a Pinterest for that same audience and they didn't bite. No one really engaged with the content on Pinterest or followed my account. So, I gave up on Pinterest and continue to focus on my Page while testing other platforms like Tumblr and Twitter