I'm kind of struggling to find a good way to describe the imaging and soundstage differences between the Susvara and Utopias as well. It's not that the Utopias have better imaging in general, it's just that it's tighter grouped because of the smaller perceived soundstage. Best analogy I can come up with is the Susvara is like a 65" 4K TV, and the Utopia is a 42" 4K TV. Both are displaying the same resolution and information, but it's easier to pick out details from the farthest edges of the smaller 42" TV because your eyes don't have to hunt back and forth as much than with a larger screen. Also, the smaller pixels can give an impression of more detail because of the smaller density. I'm hearing basically the same details from both headphones, but it's a little easier to pick out the imaging differences with the Utopias because they're closer together in the smaller soundstage. The more upfront and smaller soundstage makes the Utopias sound a little more intimate as well, and lends itself well to vocal centric music. If I had to pick a single headphone for studio monitoring / mastering, I'd probably choose the Utopia (well we'll ignore the fact that it's not closed back).
There's also an echo / phase issue (lack of transparency, maybe not wording it right here) I have with the Utopias, which is more a limitation of the transparency of it's driver type rather than actual sound reverberations in the ear cups. More of a closed in feel to the sound, like I'm listening in real life with my hands near my ears, while the Susvara (and pretty much every magneplanar and electrostat) is completely wide open and transparent. I don't hear a lot of echo, but I am definitely always aware that there is a wall of material near my ears when listening with the Utopia's. The Utopia's also do not play nice with my Smyth Realiser A8, but that's another subject I'll have to go into further detail later in my review.
It could be a gear difference, but I've been getting a lot more low-level detail out of the Utopias in my system than the HiFiMan headphones. I don't think that the Utopia seems to have better imaging because of the narrower soundstage. If that were so, the imaging would be worse. I find that, say, the singer on a good stereo recording are dead center with the Utopia, but are spread out through the center with the Susvara. Likewise other instruments locations are sharp and clear with the Utopia, and more vague with other headphones in general.