Why are there execution plan differences between OFFSET ... FETCH and the old-style ROW_NUMBER scheme?

The new OFFSET ... FETCH model introduces with SQL Server 2012 offers simple and faster paging. **Why are there any differences at all considering that the two forms are semantically identical and very common?** One would assume that the optimizer recognizes both and optimizes them (trivially) to the fullest. Here is a very simple case where OFFSET ... FETCH is ~2x faster according to the cost estimate. SELECT * INTO #objects FROM sys.objects SELECT * FROM ( SELECT *, ROW_NUMBER() OVER (ORDER BY object_id) r FROM #objects ) x WHERE r >= 30 AND r < (30 + 10) ORDER BY object_id SELECT * FROM #objects ORDER BY object_id OFFSET 30 ROWS FETCH NEXT 10 ROWS ONLY One can vary this test case by creating a CI on object_id or adding filters but it is impossible to remove all plan differences. OFFSET ... FETCH is always faster because it does less work at execution time.