What will you be using it for? I personally have plain edges on all of my Emersons, but Mr. Emerson himself actually recommends always carrying a knife that has serrations, not only because they make quick work of fibrous material, but because if the knife ever starts to go dull, the serrations will still be able to cut things. All personal preference, plus maybe some consideration as to what you will use the blade for.
As far as coating goes, I have had several EKI knives with, and several without. Currently I only have 2 Emersons, a Stonewashed Mini-Commander and a Black Coated CQC7, and frankly, as beautiful as the SW finish is, I will probably be leaning towards more coated blades in the future. The baked on ceramic coating they use is really high quality, and holds up very well, except under fairly hard use (and to be honest, I actually LOVE the look of a coated Emerson once the coating starts to come off after taking many beatings). Nothing better than looking at your blade, and being able to see a reminder of all of the good times you've had with it, or all of the times it has helped you out in a pinch, or if you own one of those really original 6s or 8s, you know... the ones made for those with truly Bad Intent, well, the worn coating probably has even more exciting stories to tell.
As much as I like Bowie style blades, I think the 8 (which is definitely a pseudo-bowie/skinner blade shape) would be my first choice over a 13. The design of the 8 is truly classic Emerson, and I am of the school of thought that the 6, 7, 8, and Commander are the Emerson knives that built Emerson (and I guess in a way the A-100 as well, since it bears a striking similarity to the Viper MV-1)
