I expected your post to generate a lot more interest than it has. I also suspect it might have been a bit of a "Dororthy" intended to add some knowledge to the group so I will add something of what I know to the pool.
A conversation with Richard Cottle early this year put me on the track of DP beans. There seems to be plenty of information about the differences between wet and dry processing but not so much about the impact those differences have on the coffee in the cup. When you look at the green beans you can make a reasonable guess about the process that has been used. Very clean and uniform equates with wet process. Not so clean, uneven, even ugly looking beans point to dry process. Other differences are easily seen when you roast, particularly in poppers. DP beans have husk and some of the dried fruit still attached been. In a popper, this is the stuff that creates the snow storm that used to cover me and everything else in the garage. You still get chaff thrown off by WP beans but it is usually a lot less than for DP beans.
Getting back to the Richard Cottle story, he explained the material coating still coating the DP beans is very effective in retaining the oils that produce crema and also adds (or retains) other flavours that can be lost in WP. This is very easy to see right out of the machine and in the Guinness effect you get in a shot glass. A good contrast can be found in the Sumatran Lintong and Brasil Cerrado some of us bought earlier in the year. The Lintong produced very little chaff and what crema was there dissipated quickly. The DP Cerrado produces enormous amount of chaff and volumes of long lasting crema. I understand the crema factor is one of the reasons why DP beans are used as the base for so many espresso blends.
There is an interesting contrast in the Ethiopian beens we have. The Yirgacheffe is a WP graded as "2". The Harrar is DP graded as "4" (or "5"). I understand the grading difference has something to do with appearance and a lot to do with taxes. The Yirgacheffe certainly looks "nicer" and more uniform than the lower graded Harrar but the lower taxes for the lower graded beans make them cheaper and easier to sell. I see the same DP/WP, crema/chaff characteristics here too. I prefer the complexity of flavour that comes from the Harrar but I dont know how much of this is linked to the DP element.
If I am making espresso, my best results come from blends with 65% to 70% DP and the balance WP. In a plunger or syphon where crema production is not a factor, I have no strong preferences and single origin WP beans can give great results.
My guesses about what I have purchased.
DP = Brasil, Harrar, possibly Java Estate
WP = Yirgacheffe, PNG Sigri, Kenya, Lintong