I also have the Progressive Industries EMS. In addition to the surge protection, it is important to get over/under voltage, open neutral, open ground, and reverse polarity protection as well. no matter what brand you buy. Low voltage can damage items with induction motors such as your A/C. If someone miswires an RV outlet as if it were a dryer outlet (240 vs 120) it can burn out every piece of electrical equipment in your B+.
Installed my PI unit in 2015 and have had several occasions where it has disconnected my MH due to low voltage in a campground. Beats the heck out of possibly burning up the A/C. If you get the PI unit, get the remote display with it too. Is cheap and it shows you the current voltage, current amp draw, and the reason for disconnecting if it detects a fault.