I always hear from experts they are not needed and a waist of money???
That's what I've heard about OEM windage trays. Few Stock class guys use trays and I have been using a dual scraper for years. I have to admit that I haven't and won't be able to do a back-to-back comparison due to time and money, but just looking at some trays, it's easy to imagine a lot of oil getting trapped within the tray because of insufficient vents. Even in the '70's & '80's, it was recommended that the "vents" be opened much wider. In my opinion, a properly designed combination of a tray/screen/scraper would be most efficient.