7on,
There have been a few posters who've provided several views and some valid advice. You don't say exactly what you want the drive for so it's not easy to know whether spending the money for 2TB (that is enterprise class or not) is worth it.
For example, you have a Mac Pro with three drives, say, a 600MG and two 1TB drives. Now you only have one slot left. If your drives are pretty full or you're thinking they'll become so soon, you probably should look at a 2TB drive for the empty slot. Or, put in the 2TB drive you purchase, transfer the data from both of your 1TB drives to the 2TB. Then remove the two 1TB drives and that will open up another slot for future expansion.
Another question: Do you leave your machine on all the time? Do you use it as a server? If the drive will be spinning constantly for the next few years, it might make sense to get an enterprise class drive. If the machine isn't used too frequently then it might be less important to go that route.
Whatever you decide, make sure you have backups of all your data. Ideally, you'd have two sets of backups. This can't be stressed enough. One industry pundit said a few years ago (Was it David Pogue?) that "There are two kinds of people: Those who backup their computers regularly and those who will."
Best wishes on your decision.
musique
P.S. I have several Macs with both 1 and 1.5TB drives, both Seagate and Western Digital. I also have a NAS in a RAID5 set-up with four 1TB drives (2 Seagates and 2 WD) and two 2TB drives (both WD). All of these drives are enterprise class. They've been running 24/7 for about a year and have 0 reallocated sectors. I may have gotten lucky.
