I wish I had pictures, but I don't. I brought along a disposable camera but totally forgot to bring it to the pizzerias. I have yet to replace the digital camera I had stolen during a UK trip in 2006.
The first thing I noticed about Da Michele was its bold tomato sauce. Looking back at that comprehensive Italian video about their kitchen, they showed the sauce being ground from a whole can of tomatoes including the puree. That might explain that. It was different from any Neapolitan I've had in the US. I don't think they add any salt.
The cheese at both DM and Costa was great. I had fior di latte at both. The crusts were saltier than any US NP I've had. It was very hot outside and as has been discussed here they sometimes control the fermentation speed by increasing the salt level. Alone it was a bit much. Surprisingly, at DM I got a generous amount of sauce. Even with the parmesan on top and the salty crust below it threw off the balance. The whole thing could have used a sprinkling of salt.
I ate my pizza at Costa (one of the little ones in the heated case, but it had just come out) folded up libretto/portafoglio style. Maybe it's in my head but the way you eat pizza changes its flavor. Costa was well-balanced but I was also eating everything sandwiched between the many layers of salty crust. I read here that Costa's dough is made with crisceto. If that is indeed the case, it is just like Marco described where no sour flavor is detectable.
The rims at both places were flatter than at most places in the US. It helps when folding into a libretto. At both there were bits of crispiness on the rim but nowhere else. DM's was easily cut with a dull knife and was not gummy. Leoparding was limited to small black dots here and there.
Overall I think it's worth tacking a day or two in Naples onto another trip as I did, but probably not a visit on its own. A food trip including various parts of Italy would have been much more interesting, I think.
I did have a bad pizza in Naples--at the airport. I figured I'd give it a try since it was not that expensive. It was made in a deck oven with temps around 650 F. I didn't notice immediately but the skin was thrown in a sheeter. It baked up flat and even after several minutes it didn't get much color (maybe using unmalted flour?). It was lousy but not offensive.
I'm not exactly an expert but I hope this is a helpful enough review.
Oh, I forgot: the oils did not have distinct flavors but maybe worked as a "glue" as has been suggested elsewhere. There was a big plastic container of sunflower seed oil (olio di girasole) in the trash can at Costa's kitchen.