Caseinate protein by itself or a caseinate/whey mix more effective?

[Lift Chief]

I'm trying to make a good during the day and before bed protein that will be slow absorbing.

I saw at proteinfactory their night time formula has caseinate and whey and soy. Would this be preferred to straight up caseinate protein?

 

[The Terminator]

Whey has a higher BV than casein or soy but is faster absorbed...The blend of all of them would be ideal before sleep, while straight whey would be preferred post workout...The blend could realisitically be used at any time though...

 

[javaguru]

I prefer to use milk isolate.

 

[Lift Chief]

I prefer to use milk isolate.

Why is that?