WLR are great primers they are typically a hotter primer than the Federal 210. I have seen up to 60 fps difference in identical loads switching from WLR's to Federal 210.
The 210 primers are regular, 210m are the best uniformed from the 210 run of primers. As stated above the WLR primers should be made of alittle tougher material.
I was told the ONLY difference between 210M's and 210's is an extra inspection. I have used both and there is ZERO difference in load performance. I buy 210's now.