With a PHP framework you

• Speed up custom web application development. ...
• Simplify web application maintenance. ...
• No need to write additional code. ...
• Work with databases more efficiently. ...
• Automate common web development tasks. ...
• Protect websites from targeted security attacks.
• Perform unit testing efficiently.

But

• It is not that secure due to its open-source, because the ASCII text file are often easily available.
• It is not suitable for giant content-based web applications.
• It has a weak type, which can cause incorrect data and knowledge to user.

If you know very good PHP, it is better to go for PHP, if you are in a harry with no ready PHP libs better go with the Framework.For 1 - 2 programmers fast in work is CodeigniterBest but a litthe difficult is Laravel, this is the king of PHP frameworks