I've used EDD a bunch when building all-vintage wheelsets and have found it to be accurate.
Sometimes you have to look for an 'equivalency' hub (e.g. almost all mid-late 80's Shimano hubs have the same dimensions).

As others have mentioned, correct rim ERD is critical, and this is where EDD falls down when working with more modern rims and vintage hubs. It just doesn't have a lot of modern rim information in the database.

Also need to make sure you identify the correct rim, as some of the model names and numbers in the database are a little off- recently had to double check some dimensions when lacing up a set of 70's Record hubs to some Wolber Alpine rims, and there were multiple possibilities in the database.