Use the white stiff drain hose. Soften it by soaking it in BOILING water. A few degrees lower than boiling, as I recall, makes a great deal of difference. When you pull it out of the water, you have to move fast, but the stuff is pliable, can take turns without collapsing, and is solid.

As for the cockpit drains, there is no room for error using hosing having less rigorous standards. From experience, I can tell you that you want no possibility that there will develop a pinhole leak as the plasstic ages - unless you are trying to collect insurance. Watch out for any hosing that has a metal coil inside it (like neoprene) to keep it from collapsing. That stuff, I fear, deteriorates because of a chemical reaction between the steel and the "rubber/plastic/whatever".