Your really not comparing oranges to oranges...Emme is a much more complex system than Arzel. Emme uses a bladder type duct closure and Arzel uses a gasketed blade, both actuated by low press/vac. If you have a lot of extra $ to spend on a lot of extra complexity than Emme is a good candidate. Emme has a lot of good user interface technology but requires a lot of post installation refining by either the HO or the contractor. Arzel can be used with web-based stats (field sourced) but is simple wiring and set-up and allows you to walk away from a properly functioning system.
Regarding your modulating furnace and 2 stg A/C, the Arzel HPP panel was designed for variable speed 2 stg systems and has been doing very well with modulating furnaces.
"When you perceive zoning not as a bandage but as an enhancement, you truly understand the dynamics and limitations of forced air heating and cooling"