I use the internet always in public libraries since 2002.
1. It's free, or almost free.
2. There are many libraries. I shop in many cities, so I visit many libraries. I go first to a shop, then to the next library. So I can use the internet in many places.
3. I don't have to bother about viruses or repair. If a hacker wants to follow me from library to library then he's going to leave more traces.
4. It's not really anonymous, but much more anonymous than a home connection. If the police may ask the personnel who used the computer on a particular day and hour, then it stops being anonymous.
5. If I'm banned from a forum, then I can register under another name and e-mail in another library.
6. Libraries can move to a new location. Then they get a new IP number.
7. You can use e-mail in the library via a virtual mail service like mail.be
8. In many libraries you can print at a low price.
9. In many libraries you can reserve a computer in advance.
10. While you're in the library you can also take the time to read a magazine.
11. In some libraries you may use a wireless connection.
12. You can ask the personnel to help you.
1. You have to travel a certain distance.
2. The time is limited, so you have to prepare it better. Make a list of what you want to do, a list of links that you want to visit. Prepare the e-mails that you want to send. Save pages to your USB stick instead of reading them immediately.
3. The computers are usually of an older type and have smaller screens and older software. Also the desk and chairs can be uncomfortable.
4. Some big libraries have many computers, placed before a window so you can see them from outside. This attracts many users, so you have to wait.
5. In many libraries they don't have the latest flash player installed, so it's impossible to use many websites, for example you can't see youtube videos. I installed a portable browser with the latest flash player on my USB stick but most people don't know how to do this.
6. There is little privacy.
7. You can forget your USB stick.
8. There can be too much cold wind.
9. There can be too much sunlight.
10. It can be noisy (cars passing by, crying babies, ...).
11. I never succeeded in downloading a torrent in a library.
12. In most libraries you don't have the highest speed.
13. In most libraries you can't install software, for example a high speed downloader, or a program to access a virtual world.
14. You can't play online games, maybe just a Java game.
15. In some libraries the same ennoying people return every day.
I'm not exactly sure what the OP is asking, it could be;
"What is the pros and cons of using the internet within a library?"
"What is the pros and cons of using the internet in place of the library?"
The correct question is: "Forgive me for speaking Arabic, but what's the plus and minus of bib-surf?"
I could think of another 2 cons:
1. The date and time of computers in the libraries is often wrong. Then the browser can complain that the security certificate of a website is invalid and then you have to add an exception to be able to access that page. If you save pages to your USB stick and you arrive home then your computer can complain that the dates of those files are invalid.
2. Some libraries have a nanny program that blocks access to some websites.
I could think of a pro:
1. You can meet new friends in the library, Arabs for example.