I am currently porting a 3.4 app to 4.1 and have 100's of lines of code like

var frmId = new Ext.form.field.Text({...});

In Ext 4.x, these calls could be converted to:

var frmId = Ext.create('Ext.form.field.Text',{...});

I understand maybe the benefits of using Ext.define/Ext.create for application classes but why use Ext.create for Ext classes?