PageBlockTable:

• PageBlockTable should be define inside apex:pageblock or apex:pageblocksection
• PageBlockTable uses standard page styles
• PageBlockTable has the required attribute “value”
• Column headers will be displayed automatically

DataTable:

• No need to write inside apex:pageblock or apex:pageblocksection
• There is no required attribute value
• The data can be displayed using custom styles
• We need to specify column headers explicitly

Repeat:

• No Salesforce styles inherited, no need to use apex:column
• Simply data displayed in irregular format
• You can have full control over rendering data