Pad composition indeed can make a big difference in wet conditions. The Motorcraft replacements for my car didn't do well in the wet until they were heated up. The originals didn't have that problem. The ones on it now (Satisfied Classic semimetalic) also do not have that problem.
The Motorcraft pads did get better as they wore, but still nothing near what they should be. I replaced them when they still had about 3/4 of the material remaining. Safety in the wet was more valuable than the price of a set of replacement pads.
