The advantage with Viper system (depending on version) is longer range compared to the line of sight Acura remote start. I could see the advantage of having the Viper system and starting your MDX if it is sitting in airport parking for 1-2 week if you are out of town. The Viper system could be handy at a park-n-ride lot and you wanted to start the MDX to heat/cool it off while you're still miles out on the bus and/or /train.
Acuralink remote start isn't available for the 3rd Gen MDXs.
AcuraLink is about as handy as a trap door in a row boat. It has NO remote start for the 2018 hybrid MDX. You have to use the key fob for "remote" (which is also pretty much hit and miss, even when the vehicle is in the driveway, 25 feet away.)