A more specific question here:

My 240v baseboard heater says it can be wired with a single or double pole thermostat. Since 240v is already "dual pole" with two hots, do I want to stick with a double pole thermostat? Are there advantages/disadvantages to each?

Thanks.

With 2 pole, it disconnects BOTH Hots. Personally, I feel it is safer, more correct.

I have to agree. A single pole thermostat on at 230 circuit isn't the best place to save a nickel.