I've been very impressed with the Jagwire Ripcord housing for my mechanical discs, the difference is especially noticeable on the rear run. Bought in a 25' roll it's a much better deal than getting the smaller one bike kits, altho still more expensive than good generic brake housing (which works very well in any case and is probably from Jagwire too). It's a compressionless housing similar to a derailleur housing, but with the kevlar reinforcement to hold it together. Had never yeard of Yokozuna, just checked out their Reaction brake cable it's also a compressionless type, but this stuff makes the Ripcord seem inexpensive.

Any housing can be well sealed if you use full housing runs (no interruptions to let in contaminants). Cables I usually get what's on sale in stainless or teflon coated stainless.