The multiple copylist feature provided with Panasonic and Toshiba XS recorders should have been standard on EVERY dvd/hdd recorder (perhaps 99 lists is a bit excessive, I would be happy with a half dozen). The problem with the Pioneers being stuck at a single copylist is it limits usability of the machines when their HDD becomes full and/or you are working on a complex dubbing project with a lot of edits. Many times I have been working on a very involved project, where its taken me a couple days to finesse the edits, when suddenly I need to quickly burn some other simpler titles off the HDD to DVD. The only way I can do this is if I erase my carefully built up copylist and create a new one to burn the quickie titles. Admittedly most normal users will never be bothered by this, but it aggravates me no end that I can't at least SAVE the complex copylist and have the option for just one more when I need to burn stuff off the HDD before I'm quite finished with my heavy-duty project.
Day to day, this has much more impact on my work than the subtle video tweaks Pioneer/Sony offered. I understand their value to SuperEye because of the variable material he collects, and I have used them on occasion, just not to the degree I would use multiple copylists. Its rare that I encounter material that is fantastically off IRE spec, and I don't find the video tweaks built into my Pioneers stupendously effective at fixing those problems. They help, I'm glad they're available, but I'd trade them in a heartbeat for Panasonic's multiple copylists and "phrase save" title entry feature. These are things I'd use several times a day, the video tweaks maybe thrice a year. At least the Pioneer/Sonys with USB sockets can accept a PC keyboard for title entry: that makes up for the lack of a title memory bank.
The Pioneer MN manual/flex record speeds are wonderful, and I would not want to trade those for the automated Panasonic FR system. The Panasonic system is one of those odd cases of automation being harder to operate than manual controls.
I really like the Pioneer HDD nav interface and mostly-intuitive editing system that never crashes or allows "illegal" edits. The Pioneer edit preview is reasonably accurate compared to several other brands which can be so far off you lose important dialog.
It is nice to have the choice of 6 menu designs for finalized Pioneer discs, I use the three-up and six-up formats most often. The four-up option in later Pioneers and the Sony 780 is hideous, but very nice in the older 510, 520 and 531 (don't know why they changed it). Speaking of finalization, I *hate* Pioneer's decision to make all DVDs have manual menu activation. No Pioneer-finalized DVD can autoplay, which confuses the crap out of everyone I give a disc to and forces me to print out little instruction slips telling friends/family that they need to wait for the disc to load, then manually press the Disc Menu button on their remote. Panasonic's auto-play menus are a better choice for typical consumer use and should have at least been an option on the Pioneers.
The HDMI on the Pioneers works predictably and reliably, unlike most other recorders. The upscaling quality is good, although I gather not quite as good as Panasonic. The 2005 and earlier Pioneer remote controllers are a marvel of intuitive handling that can be operated by feel without looking at the buttons.I stocked up on a few of these and use them instead of the random remotes that actually came with later Pioneers (the Sony remote for the 780 is similar to the older Pioneer remote I prefer). The Pioneers and the Sony 780 have a huge informative front panel display that can be read from 12 feet away (as opposed to the appallingly tiny and useless Magnavox front panel readout).
A little-discussed topic is the actual compatibility of various recorder brands with flawed VHS or Beta signal input. Over the years I have tried several brands: all, except for recent Pioneers (and Sony 780) had major or minor issues when handling VHS/Beta input. My vintage JVCs and Toshibas and very early Pioneers, would flip out unpredictably even with seemingly-perfect tapes. All the current Magnavoxes have a maddening predilection for little video "hiccups" that don't show while monitoring the dub but appear in the recording when you play it back. Recent Pioneers and the Sony 780 are bulletproof at handling tape input: if the tape is great, you get a nice dub, if the tape is bad, it will reproduce exactly, warts and all, but no additional glitches or problems will be added by the recorder (their lock on line-input is incredibly solid). Apparently the Panasonics also excel at this, although I haven't used one extensively enough to test. I'm really tempted to pick up an EH-59 while they can still be had...
Lastly, the Pioneers and Sony 780 have a nifty ability to format ordinary DVD-R or DVD+R for use as "live" backup discs for the HDD. Anything HS dubbed to these specially-formatted DVDs can be HS dubbed back to the HDD in their original editable form. This comes in very handy if you have a lot of compilations: I usually burn one finalized regular DVD and one "live" format DVD of each compilation, so that I can mix and match or update collections at a later date. In a pinch, when a Pioneer burner is failing, it will usually retain the ability to burn these "backup" discs to the bitter end (even if it can't burn standard formats anymore). This has been a lifesaver more than once, when I've had to repair a Pioneer for myself or others (you can back up the HDD contents to ordinary DVD-R, and restore to the new HDD).
I've always thought Sony erred in not continuing the co-production factories after Pioneer tanked in 2008. Granted, the only Sony that got to North America was the Canadian 780, but the Sony EU versions of the Pioneer recorders were runaway hits, the most popular in Europe year after year. It would have been great to see a Sony 790 with ATSC, and perhaps a Sony BD/HDD. But Sony chose to bail on selling top-quality recorders in the wake of the Pioneer Kuro disaster, instead subcontracting a series of truly awful DVD/HDD recorders from Samsung for their EU market. These were so terrible they made the crude Magnavox look like the Panasonic EH55, and killed off Sony's EU recorder sales almost overnight. Today Sony sells nothing in this category, and Pioneer is no more. R.I.P. - it was a nice partnership while it lasted (2005-2008).