when your somewhere that has monsoons....
I prefer the rubber topy's you can install over a leather sole. I find for me, I tend to slip often if I just have the leather sole (and this is even after I have probably broken in the leather sole). I will add an interesting point, that I recently visiting with both John Lobb, Ltd (UK-family owned) and George Cleverley and asked them which is better (leather only or leather with rubber topy's) and was given two different answers. John Lobb recommended no rubber topy's as it will not let the leather breathe and the sole may separate over time. George Cleverley said that the rubber topy's are fine and will not harm the shoe (and even make the most sense in the majority of climates and walking conditions) and that it might even extend the life of the shoe since the leather soles will not need to be replaced as often. Two differing opinions from two great shoemakers. The debate rages on!