I will try to answer my own question after some several tries and researches about these 2 visualization libraries, here are my own list of pros for each solution :
Flot Pros
- jQuery plugin : if you are familiar with jQuery (or if your apps is integrated with jQuery), it seems natural to use Flot
- Offline visualization : you can test or have it installed into an internal website. Google Visu can only work if you have acces to the google website !!
- Customization : this is basically a JavaScript file so if you are good at JS coding, you can customize your charts as your convenience. Also the Flot plugin system allows you better modularity
Google Visualization Pros
- Documentation : awesome ! Examples for each type of graphs are available in the Google site
- Easy to use : Really. Easier than Flot (that requires to somehow customize the div container)
- Powerful : you have many sorts of graphs and features (zooming, interactivity,…)
- Java and Python API : it can helps a lot for constructing the Data Table (at least for me, I can use the Java API)
Bottom Line
If you are familiar with jQuery, go with Flot. If you need for some reasons to see your charts offline, go with Flot. If you want full control, go with Flot.
If you don’t recognize yourself above, go with Google Visu. It’s easy to learn and implement, very well documented and extremely powerful.