Lumin U1 vs Lumin U1 mini + sbooster?

Well, I was able to get to try the U1 in my system this weekend.  I agree with mrcypruz, it is better - don't know why (!) But it is.  For me the difference is worth the extra cost.  More refined, better highs, most as was previously described, but I'll try it this way.  Like most good digital I've heard, in terms of upgrades, it just seems to put everything in its place better, in terms of the presentation.  It's not just a factor of sound attributes (e.g., highs, timbre, dynamics, etc.) But of a more realistic presentation.  And I think it is also in the realm of timing somehow.  As an analogy, compare a 1960 movie in Technicolor - nice looking, but a modern movie in HD looks more like the real thing.  The U1 mini sounds a little stunted in comparison.  I had the SBooster as well.  I also like the idea of being able to keep the U1 for a long time while being able to upgrade the DAC only, if desired, or like in my case presently pairing it with a great SACD player with DAC input.

Mrcypruz, thank you for your comparison, great info.  Curious - how did you compare the two?  Both connected simultaneously to DAC and quickly switching, or some time in between?  USB, coax, etc?
I have the mini and would definitely upgrade if the U1 was better.  My logical problem (without testing u1 against the mini) is using my Luxman D08 as a DAC, which is a great CD player, feeding the same 44.1 Hz file through the U1 mini, the CD playback IS better, but not huge.  So to buy the U1 to make up only some of that difference doesn't seem to be worth it. I do have a revealing system - Magico/Luxman/Nordost.
     I think my way of testing is a good test, using the same DAC via the original CD source as THE reference from which to judge.  Most people just using a DAC couldn't do this, obviously.  The CD playback presents a performance ceiling that theoretically couldn't be beaten, only strived to, and the Gap is very small in my case at least.  I wonder if the DAC receiving the signal from the streamer makes a difference, some kind of synergy issue between two different streamers?

Sounds like a varied and thorough group of tests.  I'll have to try the U-1 sometime.