Panasonic DP-UB9000 is a terrific player.
There is only one choice for a premium-built, all-aluminum chassis unit (which is the way gear USED to be...but sadly front displays and solid build quality is a thing of the past), and that is the UB9000.
However, the unit has a plethora of head-scratching shortcomings that some potential owners need to know about (especially given this thing's through-the-roof price; for the record, I own one):
First, it has a non-defeatable auto power-off function that gets REALLY annoying if you have some time, say, between discs you're loading; in my case, sometimes the dog has an accident that we need to clean up or can't decide on the second film we're gonna watch, and this sometimes takes longer than 15 or 20 minutes. The player will power off -- and also dim down its home screen before this happens, annoyingly -- after this time and there is NO way to override this in ANY setting in the menus. From what I've read, this was due to a European energy savings mandate, but that doesn't explain why Panasonic didn't eliminate this stupid feature for North American customers or customers elsewhere on the planet. Absolutely ridiculous feature.
Also, the player will not remember where you left off on ANY discs -- DVD, Blu-ray or UHD Blu-ray -- UNLESS the Blu-ray or UHD Blu-ray has been authored with the "RESUME: YES/NO" prompt, which will pop up the next time you insert the disc. If you press STOP during playback and then eject a disc, the player will NOT remember where you left off last -- something every player before the Panasonics in the 4K era did, including Oppos. This was another ridiculous thing to be missed by Panasonic.
Further, there is no power button standby/on light/indicator around or on the power button; this is hardly a make-or-break thing, but why couldn't Panasonic add one like the Cambridge and Oppo players have?
The front display is ridiculously stripped in terms of information -- all you get is a simple elapsed time for disc playback. No chapter information, audio codec data, nothing. Oppo, again, is SORELY missed in the disc player market because of touches like this...
Now -- if you're still a DVD enthusiast, as I am (I own a TON of DVDs still in our library and can't/won't get rid of all of them), this player just flat-out sucks for a number of reasons (though a lot of these will be relegated to my needs, personally). First, the Hollywood Cinema Experience processor in this thing has pretty cruddy 480i-to-2160 upconversion; I realize it's a HUGE burden on a player's processor to get 480 lines of resolution (interlaced mind you) up to 4K, but my Cambridge Audio CXUHD that I had before the Panasonic (I still have it; it's sitting in the closet as a backup because it developed a noisy DVD playback problem that the repair center couldn't fix; this player is a clone of the Oppo UDP-203) did not exhibit the artifacts I'm seeing with the Panasonic (using the same display settings, which are accurate in my television's Movie picture mode). Just like the first generation DMP-BD10A Blu-ray deck I used back in '08 or so (which I still have and use in the bedroom), the Panasonic just can't de-interlace properly, causing aliasing (jagged edges) and other problems when viewing DVDs.
But that's just the beginning: The DP-UB9000, like every Panny 4K player since the launch of their UB900 debut unit back in 2016, does not offer ANY screen/aspect ratio controls or zooming, as the player is locked in a widescreen-only output -- so if you want to watch, say, DVDs that do not have anamorphic enhancement (I still have a ton), they can't be "blown up" to be shown in their proper ratio via the Panny's remote (this was possible with all of Oppo's Blu-ray players and even their UDP-203/205...and, my CXUHD offered it too). Likewise, if you wish to stretch 4:3 DVD content to fill the 16:9 screen -- which is what I prefer, as I have a lot of 4:3 DVDs still in my collection -- you can't do it through the player; full screen DVDs will play with pillarboxing on the sides...which is technically correct on a 16:9 screen, but I loathe pillarboxing for some reason.
On a side note, we have been forced to begin buying Blu-rays and UHD Blu-rays to replace our non-anamorphic and full screen DVDs because of this zooming issue, and it's becoming pretty expensive; of course, on the flip side, it is an excuse to upgrade to the high definition version of certain titles.
Granted, I CAN use my Samsung TV's aspect ratio controls to custom-fit and blow up images as I like, but I don't prefer doing this because it's just a pain in the ass -- I'd need to go into the TV's settings, take it out of 16:9 Standard mode (which is what it typically sits in), switch it to Custom screen size mode, make adjustments with arrows to fit the image to the screen, then return that setting to widescreen once the disc I'm watching is over. Plus, by allowing for a custom zooming/shaping of aspect ratios, you end up over-zooming the intended ratio of the film, so it results in a too-focused or soft mess; it's just not worth it...I'd rather the player do this.
Then, there's also the issue of the picture adjustment controls only being available when you play a disc in the tray -- in other words, when you pop a disc in the UB9000 (or the other Panasonics, for that matter), you can access the picture adjustment controls (sharpness, noise reduction, et al) only if that disc is in and playing. Now, granted, I don't touch any of these controls (they're all on "0," the default positions, save for DVD playback, in which Panasonic has chosen the value of "2" for noise reduction and "edge correction" settings out of the box by default), but I find it odd and annoying that you can't access this menu -- even just to double check what your settings are -- unless a disc is in the drawer and playing. On the Oppo and Cambridge units, there was a Picture Settings menu that was accessible from the main setup menu, and a disc didn't have to be in the drawer.
Many of the settings of these Panasonics, too, are just overtly and unnecessary complicated and complex; case in point: There are a number of picture modes you can run the player in for each type of media you play (Normal, Cinema, Fine, Retro Cinema, etc.) plus three settings memories for each type of media (and one locked out "Standard" mode in which you can't adjust anything) plus picture mode defaults when playing 4K HDR content (Standard, Natural Environment, etc.)...it just all seems like overkill. Why not just include ONE output mode, allowing people to see what's coming off a disc, and then have a picture adjustment window for casual stuff like contrast, noise reduction, etc.?
I can go on and on about the "quirks" of this unit (and, apparently, they're shared with the other Panasonics) but there are also a number of good qualities -- build heft (for the 9000), 4K picture using the HDR Optimizer (another confusing system with a plethora of its own menus), upscaled Blu-ray picture due to the unit's unique chroma upsampling, et al.
While many will see this abundance of tweak options as a plus, it just all seems very overdone and unnecessary to me when the job of a good disc player should be to send out an accurate signal of what's on a disc (I do understand, though, that many projector owners need tweaking tools from time to time; in my case, I'm using a Samsung LCD).
I wish I could have snagged an Oppo 203 before they were off the market, but alas, I was too late; I'm not gonna pay twice as much as what the Panny 9000 costs NEW for something that's used, thus my decision to go with the 9000 for a premium, well-built option.