So I have found that these two drives and I know that the RE4 is faster. But that aside which of the two is better? longevity, known issues you cannot see from specs ect. Most of the stuff in reviews is DOA and honestly that can happen with anything.
The most reliable drive is the RE4, as it is a Enterprise drive and is great with RAID setups. I use to build only with the WD 640GB Black drive until recently. I've moved to either SSD (of course high cost) but mainly went with the Samsung Spinpoint F3 1TB. It is the faster drive, as it is based off of two 500GB platters. I've seen no reliability issues with the drive since I've been building with them. Plus, you get a larger capacity drive for less money, along with the speed.
Hands down the RE4. A small, not very well publicized fact is that WD used to recommend the Caviar Black for RAID setups. Not anymore. Apparently, when used in RAID arrays the Caviar Blacks do not recover from being taken offline to repair bad sectors, even for a little as 10 seconds.
The RE4 is a little heavier and was developed for high heat, high writes that Video Surveillance recorders subject hard drives to. That's up to 16 camera's data being simulataneous written to the hard drive 24/7. That's a constant never-ending cycle of continuous writes that can withstand being taken offline to repair or move data much better than the Caviar Blacks, and thus, do not detect the drive as having failed and triggering the array to take the drive offline and then using the global spare, provided you have one. In my case, the OS drive was marked as a global spare.(note: I was toying with the idea of using my Server 2008 as a FTP Server and I opened up ports 3389, 20 and 21, while I configured it. Later, I saw in my router I had a fellow tech from China who may have tried to help me out while I was obviously called away to din-din and inadvertently marked my C: drive as the global spare instead of the extra 1TB waiting patiently) RAID Arrays generally wait at least 1ms before it starts rebuilding the array. I saw the Restart Notice and it wasn't until I saw the RAID Manager in DOS was congratulating me on my new 10TB array, that I realized that the unfamiliar emotion I was feeling, was very similar to an earlier feeling I had when I parked my 540i on both sides of a tree simultaneously) until the reboot and then.....10 TB array wiped. Intel had tons of problems with the Intel Storage Matrix Manager up to v8.9. Version 8.8 wouldn't lose the drive. I have had almost no problem with the Intel RST losing drives and this is good.
The RE4 have an excellent reliability record. Lowest failure rate of any desktop drive. The 64mb cache drives are finally SATA III. The drive is ENTERPRISE grade and only costs $10 to $20 more than the Caviar Blacks. It matters in the long run. I have over (80) 1002FAEX, (20) 2002FAEX and (10) RE4 1TB, 6 (RE4 2TB) and I can attest to the quality of the Caviar Black drives. Never had, nor have I heard of a RE4 failure.
Make sure when you buy a Western Digital drive that you register it with WDC.com ahead of time. If you do have to send in a drive, it speeds things up. You can get up to 5 Advanced Replacements per day. Here is a heads up on one problem I have encountered twice over 30 drives. I sent in a 1TB 1002FAEX and received back a drive that was a black label WD10EZEX-00RKKA0. This is NOT a 1002FAEX Caviar Black. It had the exact same weight and design as a 1TB Caviar Blue and when I spoke to a supervisor, he immediately sent me out a 1002FAEX, shipping included and asked that I include the WD10EZEX-00RKKA0 in with the bad WD1002FAEX and to use the shipping label he emailed me. I never have a problem submitting a drive to WD. I had (61) Seagate ST3500320AS with the SD15 firmware. EVERY DRIVE THEY SENT ME EXCEPT FOR TWO, THAT THEY MARKED AS RECERTIFIED, FAILED WITHIN A COUPLE OF WEEKS. I have been just throwing them away since. Every ST3500320AS that lasted past 2 years or more, has not had any problems.
This is not necessarily a good thing, but one attribute of WD hard drives that I have experienced, is that when they have a problem, it usually shows up in your event viewer as "Disk" Event ID 7. With the Seagates, the firmware goes bad and you can no longer access the drive. Spins quiet, but the BIOS and Windows can no longer see it. With WD, the reserve space fills up and begins to save data where your good data is and that is bad, but it keeps going and and going. I have always been able to save the data and for me, that's all I am concerned about. With Western Digital, I have ALWAYS been able to recover the data, EXCEPT ONCE. That's not an unacceptable characteristic to me. At least you will be able to get your data off of it.
After Seagate bought Maxtor and began experience Maxtor's legendary bad cluster syndrome, where by the time it shows up in the Event Viewer, it's already too late. If you see one bad sector, you actually are experiencing bad clusters in the thousands range and the whole drive is gone in hours. This is not scientific, but one symptom I have encountered over and over on Samsungs, Hitachi and older 2.5" Toshiba drives is when they fail, they stop spinning. If it doesn't spin, you can't save the data. That's bad.