As others have said, I prefer photos. Perhaps marked up showing the area that is bad.
That said, realistically, the Board doesn't have to show any evidence (they should, but are not required to).
Photos lets everyone see what the complainant saw.
If challenged, proof would have to be provided to the court, so I think it's silly not to provide proof when telling the member that something is in violation.
We had an issue once where a fascia board along a roof line was not painted when the house was painted.
The Board told the owner, the owner told the painter, the painter said it had been painted.
This went around and around a couple of times until I took the time to walk to the home and take a picture.
Now the owner saw what we saw and had proof for the painter (who apparently never looked).
So, photos are the best proof.