Apache Solr string field or text field?

The fields as default defined in the solr schema are vastly different.

String stores a word/sentence as an exact string without performing tokenization etc. Commonly useful for storing exact matches, e.g, for facetting.

Text typically performs tokenization, and secondary processing (such as lower-casing etc.). Useful for all scenarios when we want to match part of a sentence.

If the following sample, "This is a sample sentence", is indexed to both fields we must search for exactly the text This is a sample sentence to get a hit from the string field, while it may suffice to search for sample (or even samples with stemmning enabled) to get a hit from the text field.