The easiest way to talk about different types of companies, especially in cases such as this in describing local vs national companies, is to pin it into an example sector. For the purposes of this I’m going to go with film. A large, national film studio would be likely to get their latest film to have a major distribution deal - theatres all across the respective country, with corresponding areas of interest getting more viewings (for example, a film set in a certain location would have more potential to be seen in that location). A local, and thus much smaller, film would have much more restricted screenings, if any at all, and likely only at small film festivals. The serious cons of national film companies is that whilst they cater for a much larger audience, films can lose their personal creative touch, swamped under a huge budget that over processes everything, but as a pro they often succeed much more than they don’t, whereas whilst smaller film companies can produce creations with a much more personal feel and integrity, they may not even make the film break even thanks to the lack of distribution and also a much smaller range of interest from the public.

Commercial companies are, obviously, profit based, whereas public companies are entirely non-profit and funded by things such as donations and the government. The most simple example possible of these would be commercial television companies versus public television companies - BBC’s television is a public company, funded by TV license fees that are given to every household in the UK, however ITV is commercial company funded by the advertisements that it displays between shows and in the breaks during said shows. There are a few pros and cons to each - people for instance may not necessarily like the fact that they’re forced to pay money to fund a television company, or may not appreciate the content, but also the fact it’s publicly funded allows for a diversity in programmes and chances will be taken. It is not to say that chances won’t be taken on commercial channels, but the programmes will be more geared to simply reeling in a bigger audience so that they can generate more money from the commercials - which they will then use to go on and create yet more programmes that are geared towards a big audience.

The USA market share of the film industry is today split between six big companies: Time Warner, Viacom, News Corporation, The Walt Disney Company, Sony Corporation of America and Comcast/General Electric. These are the conglomerate companies - the subsidiaries of these are Warner Bros. Entertainment, Paramount Motion Pictures Group, Fox Entertainment Group, Walt Disney Motion PIctures Group, Sony PIctures Entertainment and NBCUniversal.

These companies all own several well-known film studios - the best example would probably be Warner Bros., who have their own studio as well as owning New Line Cinema, HBO Films, Picturehouse, and Castle Rock Entertainment, as well as Turner Entertainment. 

This alone shows how huge the film industry is today; Time Warner is the world’s second-largest entertainment/media conglomerate company, staying behind Disney in terms of revenue. Whilst film is a major part of what Time Warner does, they cover a great many things - they own an animation studio, DC Comics, and their television ventures include HBO, Adult Swim, CNN. They also own many website services, magazines and even some radio services.

The film industry has changed and shaped itself into an entirely different and more complex beast in comparison to one hundred years ago in the early 1900s, when film theatres were just starting to exist and everything was silent. Now, those six huge companies take up a massive 85% of the market share (as of 2010), and films are complicated and branch into many other industries, often coming with video games and toys and many items of tie-in material.