I prefer the IRS, but I also have love for the straight axle. I think of it like this if you car come factory with a straight axle or you really into DR'ing then stick with or go to a straight axle. Then get rid of that 4 link crap by add a Torque Arm with either a Panhard Bar or Watts Link and dropping the upper control arms. I personally think the IRS when built right is the better choice for a badarse streetcar though. You can run much higher spring rates without diminisioning the ride quality and not all roads are smooth.