I think any DWR is good enough if you're fairly protected under tarp - nobul1, I assume argon is similar
If you get quite a bit of moisture, the M50 is much better. I puddled water on top of nobul1 and M50. After a few minutes, the water leaked through the nobul1. After as few days the M50 still didn't leak so I stopped test. M90 is supposed to be good too.
If you have rain falling on you, like a bivy without tarp, the M50 leaks, you need Event, Gore-tex, or the like. The rain drop has a large velocity when it hits fabric, which exerts a lot of water pressure, so water gets through. According to Richard, you need HH of 1500 which is greater than any of the non membrane fabrics. Although I've only tested a few.