As it stands at the moment, apart from the warranty and the reputation based on previous models, the 1tb Caviar Blue is a better drive than the current 1tb Caviar Black, in my judgement. I was just weighing out the same choice just over a week ago, and cost not even being a consideration, I went with the blue model. I suspect that soon enough they will release a single-platter 1tb Caviar Black, but there are only rumors, no ETA yet. Whenever that happens, it will likely fly past the performance of the blue again, but that's not very relevant in the here-and-now. I don't trust passmark for all their benchmarks, but I actually think their hard drive comparison chart is pretty useful. Below are the Blue, then Black, and lastly the Seagate mentioned after my suggestion.
http://www.harddrivebenchmark.net/hdd.php?hdd=WDC+WD10EZEX&id=616
http://www.harddrivebenchmark.net/hdd.php?hdd=WDC+WD1002FAEX&id=30
http://www.harddrivebenchmark.net/hdd.php?hdd=Seagate+ST3000DM001-9YN166&id=470
You can see the Seagate is a bit better in the performance arena, but not by a whole lot. I would argue with the reliability issues Seagate had with their drives in recent years, it would be crazy to trust 3tb on one of their drives. To back this up, 23% of reviews on Newegg for the Seagate drive are 1-egg (basically DOA drives or total failures), compared to 16% for the WD Black and 10% for the WD Blue.
If I wasn't going to run an SSD, I'd pickup the Blue for my primary drive in a snap. I'd just partition off perhaps 100-150gb at the start of the drive for the OS and application files so it might keep seek time down on such a large drive, and use the rest for data.