Really comes down to you. At the end of the day your results aren't going to be any different casein pre-bed, in a blend, or not. (Assuming your diets + training is on point, and getting adequate rest)
I myself tho, do enjoy drinking casein (or a blend) pre-bed because that was one of the "principles" I was taught when I started training, and I'm a routine kind of guy lol. I also think they taste better (idk if there's an actual reason behind that or not)