Factors affecting performance of a friction hitch:
1. Type of hitch (blakes, VT, distel, etc)
2. Type of cord knot is tied with
3. Type of rope knot is tied onto
4. Weight the knot is supporting
5. I bet there's more I'm not aware of
Bottom line: there is no single best type of prusik cord because all of the other factors play at least as big of a role.
Personally I prefer a real stiff and firm cord like Bail Out. I've found that softer more squishy cord like Ice Tail will flatten out against the climbing line as I descend, causing my knot to feel like it's getting tighter as I descend, forcing me to pull harder and harder on it to keep descending. Eventually I can't move it at all. Firmer cords resist flattening out and stay round, thereby keeping the surface area contact and the friction they create more consistent.
That advice isn't worth the time it takes to read it though unless you are using the exact same knot as me, the exact same climbing line as me, and weigh exactly the same as me. Better advice is to try as many prusik cords, knots, and climbing lines as you can to find the one that works the best for you.