I've got the 3DT (and mini-MEST and 'daddy' MEST lol).
Am burning in the 3DT for another few days, and can give some impressions/comparisons then.
For now, regarding the mini-MEST, I'd say it does sound like, well, a mini-MEST (as others have said), however I'd add something that I haven't heard said much:
I think the mini-MEST has a bit more warmth and body in the mids.
This is something that - for my personal tastes - I would have liked to adjust with the original MEST.
So for me, mini-MEST are really superb. You get maybe 70% of the MEST performance, at a fraction of the cost, plus a bit more warmth and body and richness in the mids.
Of course, it all depends what genres of music you'll mainly be listening to, along with your personal sound signature preferences.
With 3 DD's I'm hoping for a very textured sound with the 3DT and fascinating timbre.
I imagine it will do very well with rock, pop, hip-hop and so forth. More interesting will be how it does with acoustic, jazz, classical.
Can't wait to finish burn-in and post some impressions