I have a 2-stroy house that I want to zone, upstairs & downstairs, because currently the whole house is one zone. I have quotes to have dampers put into each supply line (16 total, 8 on each floor, all 6" lines) from 2 different contractors. One guy wants to use Arzel pnuematic dampers and another wants to use EWC electric motor dampers. Which way is better? Pneumatic vs. electric motors? Arzel vs. EWC?