I had the EZ Electric system and found it quite amazing. Even at parking lot speeds, it still feels like "Pantera" steering, just lighter. When you are driving down the road, you don't know it's there. Your steering just feels "pre-power steering" normal. I'm talking about the kind of speeds you'd be driving at in a city. It was exactly what I wanted. Once it's installed, you forget it's there.
There's only one person I know of that's installed and driven both systems, back to back: that's Gerry Romack; President of The Great Lakes Panteras POCA chapter ( https://www.greatlakespantera.com/). The web site has installation info and Gerry can be reached at: GLPanteraClub@gmail.com . I'm sure he'd be happy to give you his thoughts on both systems. On the Club web site it mentions American Powertrain as the USA distributor but I believe EZ Electric in The Netherlands will sell direct.