Like the previous poster said, any real on the tire makes them worse in rain, not better, because less of the tire is in contact with the ground.
The continental tires you mentioned don't have any "real" tread though -
They're probably fine - continental makes good tires.
As the other poster said, I think the Schwalbe Marathon Supreme's are the best - if by best cost is no object. Smooth rolling, long lasting, fast rolling to.
The Schwalbe Marathon Plus's are the ultimate flat-resistant tire, but they ride slower and their ride is far less smooth (probably not a quite ride either, but I haven't used them so not sure). Still last a long time though.
35c vs 42c is not a huge deal. Bigger should be a little grippier, but also a little slower. It's just mostly a matter of preference.