The Oppo is a universal player, whereas the Samsung and Panasonic are not, the build quality should also be as good if not better than the Panasonic, plus after a firmware update it should support DV Dolby Vision.
Where it may also win over the Samsung & Panasonic, is if their newly designed video chip has better algorithms for upscaling SD to 4K, which is always a big ask.
The Samsung’s main problem is that it feels cheap, looks cheap and is noisy compared to the Panasonic (And presumably the Oppo), so not something you will want to show off to your pals, (They probably have a better built £50 DVD player on their shelf) but as it will most likely be shoved in a cabinet it’s a good way to save money.
As to Darbee, I am afraid it’s one of those Marmite technology’s, so it’s good that you will probably be given an option with 2 different players.
I think it’s safe to say that 2017 will be when 4K HDR comes of age with plenty of TV’s, Projectors and Players becoming available at reasonable prices.
Bill