I've got a 2011 Memphis 335 Dot Reissue, an ES 339, two Midtown Standards, and a late 2011 Epi Ultra 339. I also owned a 2006 Sheraton with electronic upgrades, so I'll do a little comparison of the lot.
The fit/finish on the Memphis ES 335, and ES 339 are absolutely flawless. Stunning actually. I bought the 335 new, and haven't touched the setup in two years. Was perfect out of the box. I bought the 339 used, so can't speak to the setup, but everything else is absolutely superb. Concerning the laminated maple, these two instruments feel heavier and more solid than the others, as you would expect them to. The hardware (tuners, switches, pick guard and mounting h/w) is a lot nicer too.
My Sheraton, which I will assume is a close brother to the Epi Dot, was finished really well, felt a little lighter than my 335, but with Gibson '57 Classics, and upgraded electronics, really sounded close to the 335. I wouldn't swear that I could tell the difference, but if so, the 335 sounded a light darker.
The Gibson 339 sounds a lot different from the Epi Ultra, due to the fact that the Gibson has '57 Classics and the Ultra has Pro Buckers. The ES 339 sounds similar, albeit a little brighter that the ES 335, but the Ultra sounds _much brighter_ almost to the point of being harsh on the top end. But where the Ultra sounds good is running through a tube amp overdriven. Those Pro Buckers really come into their own then.
The build quality on the Ultra 339 while very good, is similar to that of the Gibson Midtown Standards, in that if you look hard, you will find some rough finish areas. I only mention these things to put it in perspective, when comparing $800 - $1000 guitars as compared to $2700 guitars. As everyone knows (or thinks they know) Gibson are overpriced to begin with. But as a point of reference, you will not find even the slightest finished-over sanding marks on the Memphis build models as you will with China and Nashville.
My point here is that IMO the build quality in the Nashville and China plants is approaching or at similar levels, with the parts and materials being the main difference. That makes sense, because there is a lot of competition in that space and the parent company probably spent considerable effort bringing the two plants up to similar QC levels. So, with that in mind, I would imagine that an Epi Dot would have be built with lower quality wood cuts than a Memphis Dot Reissue, have Epi electronics vs. Gibson, and have a build quality similar to Nashville, but definitely not Memphis.
Of course, all of this is an exercise for the colector because Larry Carlton on an Epi Dot can crush all of us on a Gibson 335 :)