Dell 6000D vs 9800

First of all, I'll assume you meant the 9300, as no 9800 exists.

Both computers will last 3-4 years and both will maintain decent performance, as long as you don't do something to destroy it. Under normal use, they will be fine.

Both have the ability to have the same amount of power. Just be sure to get the fastest processor and at least 1GB of RAM.

Both systems will be able to handle occasional games, even with the low x300 card. Make sure you get at least the x300 card, though.

If price is not a concern, go with a fully loaded 6000d. The 9300 is too big to carry around on a daily basis, and it is probably too big to comfortably fit on school desks. I wanted a 9300 at first, but I've decided that it's too big. I will either get a 6000 or a 600m. Anyway, if price isn't a concern, I would get a 2GHz Pentium M processor, 2GB of RAM (1GB would be fine), and the x300 video card. I would also go with the DVD-RW drive, a large hard drive (80-100GB) or a fast one (60GB, 7200RPM), and XP Pro. I would go with the same configuration for the 9300, but maybe a 6800 video card. However, since you won't be gaming a lot, you don't need the power of the 6800 card. Basically, the only difference in your case is the size.

Both systems will be equally powerful, so that should not be a concern. Both will be of the same quality, aside from what it feels like. The 9300's case is metal alloy, but I don't believe the 6000's is. However, they will be built with the same quality, so that should also not be a concern. Longetivity should also not be a concern. I have had a Dimension 4100 for 5+ years, and I put it through heavy abuse every day. It still runs stronger than most other 5 year old machines.