I am in the market for a jointer..having never owned one before. Since I have a very small shop I will most likely purchase a 6" model. I have recently checked out reviews of jointers and noticed that many modelsoffer spiral cutter heads. How difficult is the process of changing knives on regular three blade jointers? I've heard "hours" mentioned for this process. My two possible choices have come down to a 6" Powermatic jointer with regular blades and the Grizzly 6" jointer with a spiral cutting head. I think both are good tools that should last for a long time...but will the time saved with the spiral head cutters justify the extra cost? If you were buying a new jointer would it be a three or four blade head or a spiral head?