2lo4u
+1y
Edited: 7/5/2006 1:05:31 PM by 2lo4u
The 175 plus is the same as the 175t except it has a continuous amperage dial. The 175t only has five amperage settings A,B,C,D,and E. It makes it a little easier to adjust to your style. The HD i know nothing about. If your going to be doing moslty sheet metal work the 175t is all you need. If you want to do more chassis and frame work than sheet metal I would steer towards the plus model.