Personally I use LinkedIn, Facebook and Alignable.  To compare all of them together is tough.   Many SOHO businesses post their info on Facebook, so I have a Facebook page so I can reach that market.   For very large business or to get a broad network I use LinkedIn.    For the best bang, dollar for dollar, Alignable is proving to be an excellent way to focus on connecting with local business.  So the messaging is different for each platform.   I liken it a fisherman’s tackle box.   Each lure is used to catch fish, but depending on what and where you are fishing you will use a different lure.  If you’re only casting your networking line in one networking “lake” you may be catching the sweet bass but could be missing out on the big bluefin.