I'm assuming for his A/B comparisons he didn't parade them through the halls of Valhalla.
The Sine vs Triangle, and Resonance Compensation is probably going to be the biggest differences in raw character when comparing with P5r5 in 1/2 mode. That is something that will be noticeable, especially as you get into high resonance tones.
You are correct that he mentions "for the sounds he usually makes"... I did include that quote above. It's actually a very good distinction to note, because I'm sure there will be differences when certain parameters are pushed to extremes. Extreme resonance, FM, gain staging, etc. It's just that the majority of sound design is usually not pushing into those extremes, unless you're really focused on more experimental stuff, industrial, or sound effects. For the majority of bread and butter classic and modern P5 sounds, I'm guessing it will be very similar. That's my speculation anyway... I'm sure we'll see some more A/B comparisons popping up soon.
But yeah, I'm personally not all that concerned with it being an exact P5 match... I've been playing it over the past week, and it sounds really good, and I'm able to get that general Prophet vibe with it. I've got a P6 as well, and it's definitely up there in raw sound quality. I'll probably only keep one of them in long term, and so far it's probably going to be the T5, as I like the deeper sound engine.
Per Key allocation would definitely help to match the vintage P5 character. It is noticeable if you play repeated notes, particularly low octave/bass lines that are not in unison mode. Instead of layering the release tails of repeated notes with multiple voices, the Per Key cuts the tails and retriggers the same voice, resulting in significant difference in the character of bass lines, or other repetitive pulsing notes / chords. Also, when you start to crank up the per-voice variance, the Per Key allocation shows more colors. You get a certain consistency/order with per-key voice variance.
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I've been considering adding a new dedicated reverb unit to my setup. Was just watching some vids on OTO BAM this past week. Looks pretty interesting.