sxga+ is 1400 x 1050 native resolution
uxga is 1600 x 1200 native resolution
Both look superb with ClearType enabled in WinXP.
I've had terrible luck with Dell notebooks insofar as quality of construction is concerned. Oddly enough it seems that qc is worst on their higher end Inspirons.
I don't know if you're going to be thrilled with any notebook for 3D modeling or Flash. I guess it depends on how aggressively you'll use it. If there's any way for you to actually get your hands on the candidate machines to test them with the software you'll be using, I'd highly recommend it. Remember that Dell has a 30 day return for refund policy, unless that has changed. Don't hesitate to return a poor specimen. They don't age well.
Other manufacturers you might consider: Toshiba (Tecra, or even Satellite Pro), IBM or HP. Look at the specs carefully -- especially video. You can't upgrade them. (Well, that's true of almost all notebooks.) And, like I said, get your hands on them if you can. Test them on your lap, on a tabel / desk, in the kind of lighting conditions you expect to exist where you do your work. If the human factors design doesn't fit you, a notebook can be horrible to work with. If the ergonomics suit you, they can be wonderful tools. I've been using notebooks for many hours every day since they had 8088 chips in them. I've been happiest with Toshibas. But HPs look very good (haven't had any, though), and IBMs are excellent (had two that were perfect).
- Collin