Jazon for the protein shake post workout I'd prefer a whey isolate. For affordability and quality a cold filtered isolate (or other if you prefer) from True Protein or AlltheWhey's isolate. There are are numerous more expensive isolates also like Nature's Best Isopure, Syntrax Nectar, Subtance WPI.
Fast absorption is the key immediately post workout. Since any kind of whey supplement is faster absorbing than pretty much all other proteins an everyday whey mix such as from Optimum will work also. Just make the shake nice and dilute. But if you can afford an isolate go with that since this will give you the fastest absorption (and comfort, and taste).
Anuj, I really don't see the point of choosing between malto and dex since they are both so very cheap. However for the sake of argument I'd go with malto since dex by itself isn't really all that great in terms of apsorption and you can have bloating, etc. But malto by itself isn't optimal either.
BTW, according to my experience and what I've heard from a few others dex gets easier to tolerate after a while. I'm not sure if this is a real thing or that you just get used to it.
There are specific reasons to mix them allowing the combination to give faster absorption than either alone. However, any fast absorbing high GI carb is going to be better than nothing at all or a slow carb like oatmeal or something immediately post workout. I've already told you several times I think you should use them post workout
.