I would not build a motor without one. Its free horsepower, and every article I have seen it does not take until 6000 rpm to show its advantage. On some motors the difference has been shown as low as 2000 rpm. Its all personal preference and everyone has an opinion.
You can find some interesting debates about this over on the Hardcore 5.0 forum where some professional engine builders hang out. One thing that's often agreed on is to not use a windage tray during break-in of a street engine. The extra oil getting thrown up on to the cam, cylinder walls, etc., is a benefit during break-in. Of course a race-only engine doesn't care because it gets torn down often, but for a street engine... My own 347 ran with and without one, never saw a difference, but it did have a crank with profiled counterweights. And some builders recommend for a street engine just to run a high volume pan a quart low on oil; for instance a 7-quart pan with 6 quarts of oil.