As someone who's owned a Prophet 6, 2 OB-6's a Prophet 10 (still got) and a Trigon 6.. the Trigon is the punchiest of the '6' voicers by far. I would suggest a massive amount of 'I don't have that new synth so I'll talk it down vs what I already have' is going on.
Absolute nonsense.
For a start the P6 I had was gutless, utterly gutless, it sounded flat and as far from punchy as I could imagine. My Prophet 10 doing a proper bass sound (doesn't have to be in unison) is immense, it's extremely 'moog like' in the attack and has a ton of depth to the sound (even without a sub osc). Prophet 6 sounds a lot weaker on bass.
Ob6? Love it.. but not for bass, it can do bassy sounds but it NEVER really 'punches', it's much better up the other end, if the Prophet 6 had more guts it would probably 'beat' the OB-6 on bass (technically it does due to the 4 pole filter and more precise VCOs/tone where OB-6 is more airy/fibrous). Either way, neither are bass monsters and both pale next to my Prophet 10 or even my Prologue 16 (which is very good considering it's also a 16 voice poly).
So.. where does Trigon fit it? Hands down the best at bass, not only does it IMMEDIATELY have more low end in a single osc vs the other 2 6's it has a much easier ability to sculpt with the variable 3 osc that isn't just a 'dumb sub osc'. But even just 1 vs 1 osc or 2 oscs the Trigon out punches P6 and Ob6 massively, it has a proper weighty rounded punchy feel, a sound I've rarely heard in modern mass produced polysynths. Most of them flake out when pushed for bass.
Obv resonance up and bass thins (use feedback to get some back) but for the kind of bass I'm talking about I don't need much, if any, resonance.
Further and back on main topic, generally vs Prophet 6 and OB-6 the Trigon 6 is most definitely my favourite. I do LOVE the OB-6 for what it does well, you know it when you hear it, but for the other 90% of what you use an analog for it's just 'OK' vs the Trigon which is massively more flexible, inherently more 'analog' sounding with some real heft to it, and overall - outside of the special OB-6 filter modes that are only needed now and again for me - low pass to low pass, the Trigon filter is MUCH more exciting both in its 4 pole mode (it doesn't get dull and lost like the Prophet 6 ) and in 2 pole mode where it's, again inherently, far less 'wispy' and 'samey' as the OB-6.
Trigon 6 is the best of the 6's - Prophet 6 is the worst (many people all over the net have spoken about how they found the P6 underwhelming in terms of being a VCO analog poly), to me the Trigon sounds and reacts (bites/pushes/moves air) exactly like I'd hoped the P6 would when I got one many years back. Prophet 10 also has a killer sound, much better than P6 , but while it's awesome at snappy defined bass, the Trigon has a lot more going on to do other kinds of basses that sound more textured and thicker than the P10 in straight 10 voice mode (unison is awesome on P10 though), for poly type basses with sequences/arps etc the Trigon excells note-to-note with it's punchy rounded sound and 'alive' flavour coming through from the filter/drive/feedback in ways the OB-6 just doesn't even begin to compete with (here it sounds pretty but definitely flatter and lacking on the lows) and the P6 is, as said, just kinda gutless and somewhat 'static' for an analog synth.
I've had some real moogs to compare snap/punch/bass too (inc slim phatty and sub 37 and subsequent 37 - not the top of the tree but they are pretty punchy and trigon is pretty much up there with them in that respect - ob6 and p6 don't' stand a chance)
I've also had the Rev 2 (08), before I had any of these others and found it awful. The filter is scratchy, the oscs are generic and thin and the programming tedious (having to.. I mean HAVING to put movement into the DCOs with a mod slot or 2 everytime you make a sound just to wake it up gets old) and the tone is overall cold, tinny and cheap sounding (no surprise given the chips used which have very few fans on the net). There's many owners who claim to LOVE the Prophet 08/rev 2, but there's far more Ex -owners who hated the general tone of it. It in no way compares even to the Prophet 6 let alone the OB-6 and certainly NOT the Trigon 6 which is at the top of the tree tone wise from sequential (along with Prophet rev4 and OB-X8)
That said, make your own mind up but this is my honest and no-holds-barred experience of all these synths.
OB-6 and Trigon 6 are both great, but Trigon 6 is a LOT harder to get bored with, has all the flexibility of the P6 and then some with the 4/2 pole option, has a much viby-er filter, fatter sounding base tone/oscs AND also addresses drawbacks on the other 2 synths (namely - finally a real kind of 2nd LFO/polymod while still allowing 2 VCOs) and any shape sub you like to choose rather than just square or triangle like on the other 2, and the 2/4 pole option which drove me nuts on the other 2 lacking those options (I'd much rather forgoe the HPF or the OB-6s notch/bandpass to get 2/4 pole options on all synths... but on the Prophet rev2 it's a moot point that it has that as it sounds lacklustre anyway and had to be removed from all my recordings in progress and replaced with other synths).
As for can it replace the other 2? Hoodoo I think said it right, IF you can forgoe what the other 2 do especially then yes, imo the Trigon is the best of both worlds (or as near as you can get as we only have these 3 to choose from in this case), the OB-6 is def more 'special' than P6 and it's hard to get quite THAT sound or that special filter for those tricks, but the P6 is as generic as it comes and EASILY replaced by Trigon which eats it for breakfast. I do like Prophet tones but it sounds way more 'real' in my P10 rev 4 than it ever did on P6, I don't care for the HP/BP mode but you might? But even then it's still sub-par tone wise for me, lacking life and energy/presence which is why I let it go a long time back with no regret.
OB-6 style sounds can be reached on Trigon 6 far easier than on P6 due to both the 2 pole filter option AND the more 'swimmy' VCOS (everyone knows Ob-6 felt looser and more vibey to play than the over-controlled P6 even after vintage knob update) so you can get maybe half of what OB-6 does well on a Trigon (different tonality though but imo even nicer than the same old over done OBIE tone) and ALL of the bread and butter stuff from P6 and then... a massive range of stuff only Trigon can possibly do due to its extras, and if you had to have just one yes I think T6 is the best all round by far and sounds the most powerful and 'big analog' of the 3. Trigon 6 nails (modern) big analog, OB-6 hints at big analog (but sometimes misses the mark when you need more oomph and guts) and P6 completely fails at it 99.9999% of the time).. and rev 2 is not even in the same league at all. Don't let spec sway you.