I haven't used Scientific in quite a while, but back when I did it was kind of annoying with fairly old packages.
I used it because my understanding was that they test fairly heavily before releasing and so you're supposed to be getting fairly stable distro (there are probably other things they're going for with that distro too). It may have improved since I tried it last, though I think Ubuntu's main trump card will remain their overall momentum.
I'm a long-time fan of Ubuntu. Took me many years of switching between distros to settle on it. It's:
- Visually appealing
- Functional (massive number of supported packages ready to go)
- supported by most things with "Linux support" (defacto)
- has great documentation and a massive community (chances are someone's documented whatever obscure things you decide to try doing)
----> Go with Ubuntu <----