I know this is an old topic, but I saw this info on the DNS-323 wiki and decided to share it. I was trying to find the differences between H/W A1 and B1 too. Here is what I found:
the B1 has different memory chips (same basic specs), serial port is closer to the front, Soc is 88F5182.
I hope this helps. It looks like they are essentially the same.