John,
I currently own two Essences, a Stanley Clarke Signature Standard, a Dragon's Wing, and a Europa. I have a Series II custom on order.
I'd offer this ....
It really boils down, IMHO, to a few things ...
Body Shape
Electronics Package
Kind of Music You're Playing
The Essence is close to being the smallest Alembic body. It does not come with a Q-switch (though you can spec one on an order), and has only a filter, volume, and pan. It is a neck through, but without the thicker laminates of higher Alembics. I don't view this as a bad thing, merely different. I used a '91 Essence in Baghdad, Iraq from 2005 to 2006, and I can say unequivically it performed flawlessly. We played a variety of music, and the Essence handled every task. It also never failed me in the most demanding of conditions (temperatures of 100 plus degrees Fahrenheit; varying humidity; questionable voltage).
I've played some Epics, but only in passing. This being said, it is a very versatile and light instrument, along with the Alembic quality. You can't go wrong here IMHO.
The Distillate, on the other hand, has Europa electronics from what I understand (correct me if I'm wrong guys). It has the boost/cut treble/bass switches, a Q-switch, a filter, a volume, and a pan pot. It will give you a lot of flexibility tone wise if that is what you're looking for if my Europa is any indication. I can't speak to the body shape, but most Distillates I've seen have the neck pickup too close the neck for my tastes. Again, it all depends on what you're playing and what you'll use the instrument for.
Regardless of which instrument you choose, I think you'll find, as most of us here have, that Alembic produces the finest instruments we've ever played.
Best of luck,
Alan