I don't think you can compare which looks better from just one screenshot. From those two, I think US2 looks better, but if you had a lower particle multiplier in US2 (or higher in 1), I'd probably say the opposite.
I think I like the look of galaxies in US1 more as well (depending on the particle multiplier, of course), except for how the dust particles don't scale (I don't think they do that in US2 either).
But collissions, climate, atmospheres, black holes, background options, solar flares and star textures, they all look better in US2, so I would say overall, US2 looks better.