Well, it is more complicated to install the Brakesmart than a simple plug in unit. You have to unscrew one tubing nut on the master cylinder and install a tee they provide in the line. It all screws together and takes five minutes if you take your time. No bleeding required. No big deal.
You can apply the brakes manually any time you want with the typical button on the unit.
Over the years I've towed trailers of many weights and I've had them do some things I didn't like and I had to make one panic stop on a curve with a trailer. So, having the best is barely good enough in my book. And implying that it's a hassle to install, as an excuse to not look closer, is your choice. Safety is very important to me when towing. A significant improvement in performace with an extra five minute procedure is a no-brainer. Mine now has about 150,000 miles on it and works exactly as it did in the beginning. I guess you have to try one to see the difference.
I did run a Jordan, for a while, with it's complicated under dash linkage setup. I liked it. Eventually it would not shut off and when I called them they were just going out of business. It went in the trash, but while it worked it was better than the decelerometer type units. Been there, done that. Cheap is nice for things that don't matter so much.