There comes a time when specs are just that ... specs on paper. This is a good reason why (for an example) rating a Powered speaker simply by what the manufacturer puts down as the number of 'watts' quickly dissolves in today's world, especially when you find out that those watts are NOT RMS. SPL is the game changer ... for now, until manufacturers figure out a way around that too since this never measured under exactly the same 'conditions' for each manufacturer.
Having said that, when it comes to Arranger keyboards, technology does count for ease of use, operating system and such, but when it comes to sound and style, due to different techniques used to acquire good sound, the only way you can really compare specifications is if they are categorized in EXACTLY the same fields or using the same technology .... else (as an example) a manufacturer's 128 note polyphony against another's 64 note can only be 'true' if they both used the same sampling technique (straight recordings, un-compressed samples, PCM, AWM, FM, same combination of either ... etc).
KETRON uses live uncompressed sounds and samples so taking KETRON's Mexican Trumpet or Alto Sax (for an example), when you play it, if you were to try and re-create this same sound on another instrument within the same price point, you will find yourself having to 'LAYER/use multiple trumpet/sax' sounds just to obtain this 1 voice. Now, if you layered say 3 voices on your instrument to get this 1 sound, this means every time you played 1 note, you are actually playing 3 (3 polyphonic notes are being used for each key you press) where as on the KETRON, for this same rich sound, only 1 note is being used. So if you play a cord of 3 notes, you are actually using 9 whereas the Ketron is only using 3. So in general, the KETRON's 64 note polyphony (when translated to other manufacturer's) is about 192.... or more when you now add the style engine!
Now, remember too that when it comes to AUDYA, even though it has 192 note polyphony, most of this is focused on the lead/right sounds, 5/10 MIDI tracks of the style and manual left sounds (oh by the way, the Audya is capable of playing 2 Lower/Left sounds (determined by the style) plus a dedicated independent LEFT voice (3 Left voices in total). Now since most of the styles are AUDIO styles, the Drums, Bass and Guitar tracks (in most cases) are NOT using up any polyphony (where as in another arranger, the Drums and Guitars are each consuming about 30 notes at a given time (when you factor in SUSTAINED/CROSS OVER notes)! Add that up during an entire performance and you quickly realize how 'unfair' it is to compare another Arranger with AUDYA when it comes to Polyphony ... simply because the AUDYA has more 'room' to work with, with less 'effort' to create equivalent sounds.
Now when it comes to Hard Drive (Standard AUDYA) or Solid State Drive (Audya AJAMSONIC), here is a specification with a level playing field and whose advantage you can feel and experience regardless of which arranger you are using. The SSD is noticeably faster and more reliable, regardless of the hardware you are using. USB (1.0 versus 2.0) again is a level specification which is actually noticeable mostly when you're at home transferring huge volumes of data to an from your keyboard - on the stage during performance or in the studio during recording sessions, the difference between USB 1.0 and USB 3.0 is hardly/barely noticeable. As for memory, again the technology makes a difference. As far as AUDYA goes, since it streams AUDIO from the HD/SSD (Korg Kronos does similar), having a large memory is not as vital as is the case with other arrangers. But if you are someone who depends a lot on custom sounds, extra memory won't hurt.
At the end of the day, when you create your musical product, the specs are not what created it (be it a live performance on stage or recording in the studio). I have yet to hear someone shout out to a keyboard player on the stage ..."man, you sounded great because your keyboard has USB 3.0 or fire wire or Dante or ....", nor has anyone said to a studio Engineer "this musical recording from XXXX sounded great because the instruments used to create the track had a SSD and D-Beam.
When manufacturers get to the point where specifications can be standardized FAIRLY (e.g. as was the case with GM), then specs will once more be ... what they used to be.
Just my 3cents until that moment comes .... :-)