Apache Solr string field or text field?

In apache Solr why do we always need to prefer string field over text field if both solves purposes?

How string or text affects the parameters like index size, index read, index creation?

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.

Adding to Johans Sjöbergs good answer:

You can sort a String but not a Text.