diff --git a/src/Plugin/migrate_plus/data_parser/SimpleXml.php b/src/Plugin/migrate_plus/data_parser/SimpleXml.php
index 0d6eb9ec49dcf78c838435109c84e32cfd15d4be..5f86b8bc09f0601f1889fa5969137406e9958b66 100644
--- a/src/Plugin/migrate_plus/data_parser/SimpleXml.php
+++ b/src/Plugin/migrate_plus/data_parser/SimpleXml.php
@@ -10,6 +10,11 @@ use Drupal\migrate_plus\DataParserPluginBase;
 /**
  * Obtain XML data for migration using the SimpleXML API.
  *
+ * SimpleXML parses the whole file into memory, which allows using XPath
+ * expression in the item selector. For large XML sources it results in
+ * consuming lots of memory, which can be undesirable. If you run into memory
+ * issues, then consider using the 'xml' data parser.
+ *
  * @DataParser(
  *   id = "simple_xml",
  *   title = @Translation("Simple XML")
diff --git a/src/Plugin/migrate_plus/data_parser/Xml.php b/src/Plugin/migrate_plus/data_parser/Xml.php
index ead05917b9eb17138a3766c2966727510637b17c..580df846941c498fa3394c914ef18675fde0327f 100644
--- a/src/Plugin/migrate_plus/data_parser/Xml.php
+++ b/src/Plugin/migrate_plus/data_parser/Xml.php
@@ -10,6 +10,11 @@ use Drupal\migrate_plus\DataParserPluginBase;
 /**
  * Obtain XML data for migration using the XMLReader pull parser.
  *
+ * XMLReader reader performs incremental parsing of an XML file. This allows
+ * parsing very large XML sources (e.g. 200MB WordPress dumps), which reduces
+ * the memory usage and increases the performance. The disadvantage is that it's
+ * not possible to use XPath search across the entire source.
+ *
  * @DataParser(
  *   id = "xml",
  *   title = @Translation("XML")