I only know what my own experience has given me. Leather pants work ok at first but, believe me they will retain water and wet leather weighs a TON! Great for muscle building... not so good for energy. I'd consider rain pants if not doing rubber (which is heavier). Something like good golf or motorcycle rain gear.
When it comes to boots, nothing beats good military jump style boots. They're high on the leg, laced from bottom to top, and not all that heavy. When doing caving, which deals with underground water, bat guano, and mud that's more like the clay people make statues from (super sticky)... we would put on the socks then plastic bags over them, another sock over the bag, then the boots. This kept the feet dry which is paramount. We did the same thin when doing military cross country marches. Invariably the Drill Sargent would spot a pond, stream, river, bog, anything wet and horrible and march us through it. You learn quick how to protect your feet.