There is a problem with metafile exporting. When you are saving the same chart as metafile produces files with sizes from 1,432KB to 3,883BK depending on EMF type - which in worst case was about 105 times bigger than .PNG! Doing the same test with more sophisticated pie chart resulted in .PNG file of 58KB and metafiles 7,869KB (for EmfOnly) and 20,246KB (for EmfPlusOnly).
Please see next example for reproduce the problem: 
        public Form1()
        {
            InitializeComponent();
            InitializeChart();
        }
        private void InitializeChart()
        {
            tChart1.Import.Template.Load("C:\\pie.ten");
        }
        private void button1_Click(object sender, EventArgs e)
        {
            tChart1.Export.Image.PNG.Save("c:\\teeChart1.png");
            tChart1.Export.Image.Metafile.EMFFormat = System.Drawing.Imaging.EmfType.EmfOnly;
            tChart1.Export.Image.Metafile.Save("c:\\teeChartEmfOnly.emf");
            tChart1.Export.Image.Metafile.EMFFormat = System.Drawing.Imaging.EmfType.EmfPlusDual;
            tChart1.Export.Image.Metafile.Save("c:\\teeChartEmfPlusDual.emf");
            tChart1.Export.Image.Metafile.EMFFormat = System.Drawing.Imaging.EmfType.EmfPlusOnly;
            tChart1.Export.Image.Metafile.Save("c:\\teeChartEmfPlusOnly.emf"); 
        }
Also, I have attached file pei1.ten, because you could reproduce exactly the problem.
It occurs with last version 4.

 [created:2010-05-28T11:31:20.000+01:00 reported by:sandra@steema.com reported in version:]