We use all of these products.
Indeed is more expensive and LinkedIn licenses are not given to everyone in our company.
Indeed is probably our favorite, as it has the most brand recognition, so most people use
Indeed to view jobs and apply, and when they get an email from
Indeed they seem to know they probably applied for a job there, so they will open the email.
Bullhorn is easiest for our company to post our jobs from as it is more internal.