Well, you should have a backup solution no matter WHERE you are! OK, lecture over!
It depends on how much stuff you have. A DVD solution for fairly static stuff like images and videos is probably OK, and with the "no moving parts" nature of the solution, it is impervious to mechanical breakdown. However, you can only get about 4 GB per DVD right now, and even with good compression, you can't get more than about 10 GB on the DVD. This means multiple DVDs if you have more data than that.
The hard drive solution has the advantages of capacious size and great convenience, but the disadvantage of potential unreliability.
I solve this very issue by using TWO hard disks. I have a "rotating backup". Two identical external hard drives. I keep one at work and one at home. Every time I make a new backup on the home drive, I "rotate" the two, so that the most current backup is always "off site". With two of them, you now need three disks to fail all at once (your primary hard drive and both of your backups) before you lose data. The likelihood of this is very small, hence it is a fairly reliable solution. PLUS, you have a copy of your data away from your residence, so in the event of a disaster (flood, fire, theft, etc.) you still have your data even if your computer and your home backup are destroyed, damaged or stolen.
It is these later considerations that caused me to go with the two disk approach. Now I know I could do the "two copies" thing with DVDs, but the convenience factor made me stay with hard drives. I am backing up well over 20 GB of data each time. For me at least, I find that backing up isn't easy to do, I won't do it, and hence the hard drive approach works for me.
It goes without saying that Leapard's Time Machine backup sounds like the IDEAL solution for folks like me - totally painless backup as long as you can dedicated an external drive to it. Looking VERY forward to Leapard.
Conclusion: keep at least two copies in two separate physical locations. Then select DVD if you don't mind the hassle of burning several DVDs per backup, or select disk if you do.
