The Sitecore ContentSearch Linq API provides several methods that can be used to search against string fields in different ways:
From the doc site I have been able to get a vague sense of the purpose for each and I have successfully used some of these in the past, but I have not found a clear comparison anywhere. When should I use each of these methods? Is there a significant difference in performance between any of them? Is there any notable difference in how they behave with different search providers?