When hosting on EC2, should I use FS to store files "locally" or s3fs to store files on my s3 service "indirectly"?

I'm hosting a node.js express application on EC2, and i'm using Amazon's S3 storage service.

Within my application, hosted on amazon, should I write the files locally (since the server is already running on aws) or should I still use the s3fs package to store the files on the S3 service as if I'm on a remote machine?

Thanks all!