Opening forms using C#. Is one way better than another?

What is the difference between opening a form this way:

if (ViewGLDistributionsForm == null)
{
    ViewGLDistributionsForm = new frmViewGLDistributions();
}
else
{
    if (ViewGLDistributionsForm.Created == false)
    {
        ViewGLDistributionsForm = new frmViewGLDistributions();
    }

}

ViewGLDistributionsForm.Show();
ViewGLDistributionsForm.Activate();

Select allOpen in new window

...and opening it this way?

using (frmLookupBatchIDs LookupBatchIDsForm = new frmLookupBatchIDs(batchNumber))
{
    if (LookupBatchIDsForm.ShowDialog(this) == DialogResult.OK)
    {
        LookupBatchIDsForm.Show();
        LookupBatchIDsForm.Activate();
        LookupBatchIDsForm.Focus();
        batchNumber = LookupBatchIDsForm.CellValue;
    }
}

Select allOpen in new window

I am still learning C# and I see multiple ways to open forms. Is there a proper way or is one way better under one set of circumstances and another way better under another set of circumstances?