In the opening words, I think it is appropriate to correct your mighty misconceiving, Open source does not necessarily have to mean free.
What does it mean by open?
It means people can see the source code, have full access to the hardware underlying the system and edit or control them.
Android is open source, however it is absolutely not free (the Phone companies have to pay some fees to Google Inc. for using its Android System).
Here are some examples of open and closed systems:
Open system: Linux, Ubuntu, Android.
Closed system: Mac OS, Windows, iOS, Windows Phone.
I will discuss the pros and cons of Open System vs. Closed System in the following aspects:
The closed systems are more likely to have a better UI design and to be more user-friendly, because the user pays for the system, thus the companies get motivations to improve and innovate their products. In addition, the closed system companies have to do better to compete with other systems on the market to make the users willing to pay for their products.
Mac OS has always been the most advanced and innovative as well as greatest in ease of use system.
On the open side, although Ubuntu still has a lot work to do to catch up Mac OS, it has been trying its best to make itself easy to use, beautiful and user-friendly.
Open systems let geeks do anything they can imagine. They could edit the system source code and recompile it. They have more control over the system hardware, which means they could change the hardware behaviors. Most importantly, there is no inspection, so they can develop whatever they want. But this also bring up some serious disadvantages. The hacker may edit the system registration settings to make the hard drive and CPU doing massive job and stop your fan from working. As a result, your device will gain much heat, and would probably burn even though there is self-protection function in your power supply.
Closed systems, on the other hand, may not let you gain full control of the system or hardware, but they are most likely to provide you with some APIs to have some decent, managed, limited control over them, such as changing iOS status bar, getting information from the GPS model, catch the data of the gravity sensor, and control the LED light. In addition, the third party apps on iOS can only run in its sandbox, which means it cannot communicate with other applications or altering the system behaviors.
Therefore, the open systems has more scalability but the closed systems are more safe to use.
On one hand, many open systems are rock solid, since the idea of more minds creating better software. “Open-source programs always include source code for those interested in peering into how the program does what it does and possibly contributing to the development effort” (Damicon, “OPEN vs. CLOSED SOURCE”, http://www.damicon.com/resources/openvsclosed.html). Examples include the Apache web server, Linux operating system, SendMail email server, and MySQL database.
On the other hand, closed systems are also very strong, since the revenue keeps motivating the developers to improve and strengthen the systems. Examples are Mac OS and Windows. Apple and Microsoft innovate their systems every one year or two to make their systems more powerful as well as user-friendly. They also distribute subtle updates or patchers improve their current systems’ performance and robustness.
Therefore, there is no difference on robustness over open and closed systems.
First, As what I said while talking about Scalability, altered systems or softwares may make your hardware ‘burn’. Second, those systems or softwares may also thief data from your hard drive. What’s more, there are some illegal apps in the open source application market for its lacking of inspection. I believe you certainly can find porn apps in the Android market, but there’s surely none of those on Apple’s app store.
Therefore, closed systems are more secure than open systems.
Ubuntu and Mac OS are the most known open and closed systems respectively, and Ramesh Jha has given a more detailed comparison of the two OSes specifically. Move your step to his article Ubuntu 11.04 vs Mac OS X to read more if interested.