We should evaluate the performance of job sites based on job industry, geography, the kind of candidate database they have e.g. blue collar vs white collar, junior vs senior profiles, etc.

There are leading job boards in the world like LinkedIn, Indeed, Monster that serve many geographies and many industries but they may not always be the best for every job sector, every industry and every kind of job profile.

Free job posting sites will let you advertise jobs for free. These jobs will be shown to candidates in the order they are posted. Some free job boards also offer paid job ads. 

When you opt for paid job posting, you can make sure your jobs ads are always shown on top. Also, some of these job sites could also leverage other job sites in their network. This will allow them to reach millions of candidates. 

Some premium job sites only allows paid job posting. They only way you can post jobs to these sites is by paying money.

CVViZ has integrated with 1700+ such paid and free job sites. CVViZ offers paid job posting at discounted pricing.

Job posting is basically a job advertisement that company decides to post on various platforms so that it can attract active and passive candidates to apply for the job. 

Job bidding is primarily internal job position or internal job mobility. It is open to the existing employees of the company who want to take up new role or new kind of work. 

Job bidding could be open for external candidates which is nothing but job posting. With job bidding company give their current employees an opportunity to make a move in their career. However, they could be competing with external candidates as well.