I can't speak for the Susvara in London CanJam as I don't know what it was driven by but from the little experience I've had with the Susvara (3 times in the past 3 months - 2x at shows, 1x Hifiman office), as mentioned in the Susvara thread I believe it's particularly sensitive to what's driving it. If the amp isn't powerful enough to drive the Susvara it can sound very underwhelming. In my correspondence with some folks, even something like the EC Balancing Act wouldn't do it justice as such at least in the shows in Tokyo the Susvara was driven by the EF1000. Often one would read about trying to have the Susvara driven off by a speaker amp taps via the HE-Adapter.
Having clarified that point, assume the Susvara is being driven "properly", personally I find the Susvara and Utopia to be rather different and can't say whether one is better than the other technically - however tonally their signatures are different and that'll be up to the listener's personal preference. I actually feel the Susvara to sound more on the wholesome warm side of the fence whilst the Utopia to be more tonally balance. I didn't find the Susvara to sound bright nor thin (which was what lead me to think if it was the amp used in CanJam, but again, I wasn't there).
I don't have the Susvara but I've had the Utopia since Dec '16 and in my little public and private Susvara demo sessions, from the tonal signature perspective I think they both compliment each other. It's more the technical qualities that I'm more curious about the Susvara vs the Utopia.