Where to deploy frontend files? Style Library vs _Layouts folder

I'm not going to repeat the stuff you already familiar with. The goal of this post is to summarize some findings and make a personal conclusion based on experience without requirement to read a lot.

Where to deploy css and JavaScript files? Basically we have 2 options:

• SharePoint layouts folder
• "Style Library" document library

Style Library benefits:

• Resources are limited to site collection
• Smart caching (if it was deployed)
• Ability to update it on couple of front-end servers (after that you can't deploy new version of file without resetting to site definition) through UI
• Style Library in URL looks prettier than _LAYOTUS (at first look)

Style Library Problems:

• Frontend guys are not really good in merging of .spdata files
• Frontend guys are not really good in modifying path attributes in Elements.xml
• Actually you need to be prepared to spend 10-50% of your time helping to Frontend guys
• Deployments during development phase are painful
• If file was updated manually on production you will forget to reset it
• Lower performance
• It's really annoying
• Caching is not as smart as you might think. Especially with custom NLB.

Layouts folder benefits:

• Easy to use, straightforward
• No iisreset/application pool recycling required. You can modify files directly in 14 hive, then Ctrl+F5 and voila!
• Deployment issues? Forget about them.
• Merging issues? Forget it
• Better performance
• You can be sure that nobody modified your files manually. Sometimes it happens.

Layouts folder Problems:

• Not scoped. You need just to organize your files
• Caching. More on that later (few days hopefully)
• Ugly URLs. More on that
• Sandbox solutions. Probably it won't work there. But I haven't really worked with them because I don't see any value in Sandbox solutions at this point.

Conclusion: use Layouts folder for your frontend files and be happy with SharePoint. Don't make things more complicated than they are.

Interested links:

http://sharepoint.stackexchange.com/questions/2219/css-files-in-layouts-or-document-library?lq=1
http://www.sharepointnutsandbolts.com/2011/11/avoiding-bugs-from-cached-javascript.html
http://www.sharepointnutsandbolts.com/2009/05/optimization-blob-caching-and-http-304s.html