Setting up advanced search results
Use the default Magento search- select No to enable the advanced search by SKU, color, price, etc. You have to mark values in a list only. In case you choose Yes, the search results in Ajax Search and Autocomplete search box will be similiar with the results on Magento search page.
Use custom collection on search controller- we recommend to select No. However if you are not satisfied with search results, you can try using a custom collection.