I haven't built with Engelman yet but I have a few select sets that have truly excellent stiffness to weight, and a nice taptone. It is remarkably similar to Euro. I think I can tell them apart in some cases, but not all the time. It is something about the medullary rays, a finer difference than I could explain with words. It is generally said Engelmann it is whiter than Euro, but fact is a lot of Euro can be just as white, so this falls. Perhaps the sapwood can have a more repulsive smell than Euro, imo. It is also said Engelman has finer and more uniform grain than Euro, again utter BS if one has a good Euro source.
They also say Engelman is lighter, and perhaps it is true in general, but Euro just as light is not exactly a big rarity. Anyway, it is certainly a great tonewood and I will use when its time comes. As they say, if the tree/set is good, species doesn't matter.