I got the Holden one and I was really impressed with the fit and finish. I really looks like it is meant to be there. I got a well known brand one in my 50 and it is no where near as good as the Holden one. At the time I said i didn't really care which liner I got as its only a piece of plastic. The tail gate inside cover is a good fit and looks just as good as the liner. Maybe I got a good installer or maybe they improved them. Happy to take a photo for you smergen if you want.
Mine needed more screws fitted to keep all the gaps closed plus they threw the tie down eyes away and tried to tell me you can't have them with the liner fitted ! They had to get better ones after I told them they were trying to bu$&sh$/ me .
Maybe it was the fitter but I'd still go the ARB for me .