From what I have witnessed, I think that signature campaign is more effective because most of people from Bitcointalk have decent knowledge about Bitcoin. In social media, it is very hard to find someone who knows about cryptos so that it is kinda useless and waste of money. If I am a marketing manager, I will never ever make a social campaign about bitcoin-relate services.
That is certainly true, but I see that it all depends on the target that they seek. For those who do that all have different targets and sometimes they do the right thing. not forever signature gives a positive impact for those who hold and not always social media give positive impact, it all depends on how we use media that we are very strategic. So, think back to everything before deciding something so that the results obtained are more optimally