I must have watched at least 20 reviews and install videos on YT while deciding on what to order. I ended up going with the MX4, and am very happy with it. I installed it on a colder day, and the texture of the spray in liner doesn't do much to promote adhesion of the front foam gasket. I installed it a couple of weeks ago, and it has been through a couple of rain storms and a car wash. Minimal leaks at the front corners, but otherwise the bed was dry. Most of the time I will just have my golf bag in the bed, along with a soft sided samsonite golf organizer (shoes, balls, towels, rain gear, etc).
After seeing the small amount of water that got in, I am fairly confident that my stuff will stay dry. I'm on the fence about getting the BedRug mat (not the entire thing) just to get stuff up off the floor of the bed. Time will tell.