I did some performance test between Laravel query builder and eloquent. Query builder was much faster with various of sql statement (select-update-delete-insert).
So my question is: Why someone uses Laravel Eloquent against plain query builder?
Eloquent is Laravel's implementation of Active Record pattern and it comes with all its strengths and weaknesses. It is a good solution to use when you process a single entity in a CRUD manner - that is, read from database or create a new entity and then save it or delete. You will benefit a lot from Eloquent's features such as dirty checking (to send SQL UPDATE only for the fields which have been changed), model events (e.g. to send administrative alert or update statistics counter when someone has created a new account), traits (timestamps, soft deletes, custom traits) eager/lazy loading etc.
But, as you already know, it comes with some performance price. When you process a single or just a few records, there is nothing to worry about. But for cases when you read lots of records (e.g. for datagrids, for reports, for batch processing etc.) the plain DB is better approach.
For our application we are doing exactly that - using Laravel's Eloquent in web forms to process a single record and using DB (with SQL views) to retrieve data for grids, export etc.