I don’t own either but have been very interested in the R8 for a while. At the NRA convention I handled both and got a detailed demonstration of each.
The R8 is a more developed system with a lot more caliber and barrel options. I liked the straight pull of the R8 and the trigger is phenomenal.
The 404 has a four weight adjustable trigger, but I’d think you’d pick one weight and and go with it. I liked the sling swivel / tool. Always with you. I also like the fact that if you lose the magazine on the 404, you can still operate it as a single shot.Whereas with the R8 if you’d drop the mag on the R8, you have have an non functioning rifle until the mag is inserted and if you lose the mag, you’re screwed.
The 404 actually felt a little better to me, but personally, I still lean toward the R8 due to the options, popularity and availability. But... the 404 is a sweet rifle.