Never owned the BHID 300, but I did on a BHID, while it is a good water detector in of itself, when you compare it to the Excal it falls far short....
I have never seen any of my excals or sov gts fail to identify a piece of iron as iron as soon as I swept over it, but I have had it tell me there was a gold ring beside a piece of iron The gold ring and the tiny piece of iron was recovered in the same scoop... I had a solid null from one direction, and a good gold signal from a sweep 90 degrees off the original sweep...
If I hace a BHID 300 and an Excal in my van at the beach the BHID would never get used, not because it is a bad detector perse, but because the excal is so much better...