How do I count the ways? Bass depth and transparency. Inner glow and richer texture of mids. Silkyness of highs. Better more natural boundaries of musical objects.
Much better handling of digital glare (in fact as good in this aspect as I have heard on digital and amazing still not being rolled off or sacrificing resolution). Better layering and placement of sounds. More natural overall.
I used the Hugo for almost 2 years and liked it, but right out of the box the TT was a different animal.
In many approaches to redbook digital over the years, digital fatigue and glare is often approached accompanied by a queasy-like softening of the upper bass and lower mids (I could name some high end ones that do this).
The Chord TT somehow avoids this terrible trade-off, and that really impresses me. Therefore you can use headphones (or speakers I would guess, too) that would normally be too intolerant of digital recordings that have glare or shrillness or sound peaky.
I can use all my headphones without EQ, which I think is a major achievement.
The Hugo, subjectively was more forced and I did use EQ many times.
For what it's worth, although it's reported that the Dave is a league ahead of the TT and I have not heard it, I'm so comfortable with my TT I'm leaving well enough alone for quite awhile.
I was planning on trying the Yggy, the Pavane, even the Dave, but I never got around to it because I'm just very happy with the TT, a lot more than I expected.
I do use my own amps though for the best sound. The TT really scales with better amps and cables, but that's another story...
Any gear be it DAC, amp or headphones that needed EQ to be enjoyable and musical in any of my listening-for-pleasure would be an absolute non-starter. So, for me, being able to use all my headphones without EQ isn't something I'd consider an achievement of any kind - it's a simple requirement for them to even be a consideration in the first place.
Not that EQ can't improve various aspects of some headphones - but if it was needed, nope. For mixing (or checking a mix at least), sure, for listening - not for me.
Those differences do sound signifiant - and you make them sound a lot bigger than I would have expected for a modified power-supply and some tweaks to the output stage (as I understand it the FPGA, code and filters are identical between the Hugo and the TT). I figured most of the cost increased cost would be eaten up by the case
I'll be interested to see how it fares.