// Did that sound complex enough? :) Statistics and trying to do comparisons can often be misleading as just seeing the numbers below can prove. The numbers are from a test +Wil Wheaton did: he asked people on #Facebook  and #Google + to following a list to his blog as a test on how much traffic he gets from either #network . Here they are:  

Facebook followers: 95K
Google+ followers: 1.4M
 
Traffic from Facebook:  ~13,428
Traffic from G+: ~11,261

Interactions on Facebook: 1118 likes and 345 comments
Interactions on G+: 647 +1s (same as likes) and 247 comments

On first look, FB looks like an amazing way to get engagement given that there were more interactions with just tiny fraction of followers. I think a crucial explanation for these numbers is that every like and comment on Facebook generates a story in the feeds of the friends of the user who made the like or comment.

This allows a much bigger spread of anything that get a good amount of likes/comments (as recently proven by the recent "help me get laid for 1 million likes" story http://cnet.co/YMy5pc). Meanwhile, the main way for something to spread on G+ is shares and the trending list (although usually in order to get on the trending list you need a lot of shares).  

Where as a percentage of the 1.4mil of G+ followers might see Wil's post just once if they have him on a circle which shows 100% of posts in the main stream (and if they read everything on their stream), on Facebook, it's not just a percentage of the followers who see a post in their feeds. It is also the friends of everyone who liked and commented on it through the "X commented on Will Wheaton's post" stories. 

An additional insight: a small page I manage on FB has just over 1100 likes. The overal potential audience though (friends of fans) is over 400k. I suppose some similar numbers apply in Will's case. His 95K followers can translate to an audience of millions. I wont do the math because I am probably going to end up with wrong assumptions again. 

The fact is, people interact differently with content and also discover differently  content on either network. So the whole situation is a bit like, well, apples and oranges :) 
_(Photo by Michael Fawcett http://bit.ly/12k6EE1)_
cc +Robert Scoble as he has written a lot about the differences between FB and G+ and their content discovery models.