Blah, I was hoping not to find this topic.
I too have weighed the hard drive, and am dieing to go with the HDS723020, mainly because of the reviews and extra cache. Not to mention, I find it hard to pay the same amount of money for a lesser hard drive with worse reviews.
Judging by the compatibility for the brand, and the extra compatibility of the 3 TB drives. I'm simply forced to experiment with these. I won't knock Synology if it doesn't work, but I would like to see their testers? successfully test the compatibility of the drives in a reasonable fashion, as I ordered my first Synology nas today, and am currently hoping for great things.