Go beads, I'll let everyone else explain why.
As for the hygro, they are suspect because they rely on springs to measure the humidity (honestly I have no idea how that happens, just what I've been told). However, the primary issue is not that they read X% off, it's that they can change the variance at any time. Therefore, you could salt test them on a monday and have it only be off 3%, but on Friday it could be 12% because something has stretched out on the inside and you have no way of knowing. You can continually salt test it, but that's a waste of time, when the problem can be fixed by spending $25 on a nice digital hygro. That's my take on the analog/digital argument
and oh ya, nice lookin humi
