Modelの意義が掴めない

WicketのModelの使い方がよくわからない･･･
よくわからんが、とりあえず自分用にメモメモ。

/* 正解 */
public class EditPage extends WebPage
{
	/** Creates a new instance of EditPage */
	public EditPage()
	{
		add(new EditForm("editform"));
	}
	
	private final class EditForm extends Form
	{
		private Comment mComment;
	
		public EditForm(final String componentName)
		{
			super(componentName);
			
			mComment = new Comment();
			TextArea ta = new TextArea("textarea", new PropertyModel(mComment, "text"));
			add(ta);
		}

		
		public final void onSubmit()
		{
			String comment = mComment.getText();
			
			DB.insert(comment);
		}
	}
}


/* 間違い */
public class EditPage extends WebPage
{
	/** Creates a new instance of EditPage */
	public EditPage()
	{
		add(new EditForm("editform"));
	}
	
	private final class EditForm extends Form
	{
		private TextArea mTextArea;
	
		public EditForm(final String componentName)
		{
			super(componentName);
			
			mTextArea = new TextArea("textarea");
			add(mTextArea);
		}

		
		public final void onSubmit()
		{
			String comment = mTextArea.getValue();
			
			DB.insert(comment);
		}
	}
}