Much of this relates to battery consumption. Lithium batteries have a longer life. I put pouches of silica gel in this to keep DATs, mics and other sensitive stuff dry. If you shuffle between warm and cold environments, be careful of condensation building up. For voice, they are fine.
Cassettes are okay to.
The DAT just will make your life easier for editing later. The portable DAT recorders function pretty well down into the depths of cold. So internal batteries are fairly useless, outboard battery packs de rigeur. When you CAN run on internal rechargeable batteries, the heat they give off will help. Take four or more times as many batteries as you would for warm weather recording.