It's always difficult to answer a subjective question like this. Better by what measure? Speed? Freedom? Support? User Experience? Hardware support?

I am very partial to Ubuntu, but like any other Linux distribution, it isn't w/out its headaches. Though, again, as is the case w/ most Linux distributions those headaches are often created by hardware and software vendors, and not Linux or the distribution itself.

To be completely honest with you, If your concern is going to be support is broadest sens of the word, Windows may still be a safe bet. It at elast still has the largest following out there, and the largest number of available trained technicians. A lot fo hardware vendors still only provide their drivers for Windows and a lot of software companies still only code for Windows.

That aside, though, if your concern is ease of use, I would have to say that Ubuntu would give Windows a run for its money, on most hardware these days.

If your concern is stability, There is little software out there as rock solid as a Debian stable release.

Performance can be a funny thing, too. I can turn on every wiz-bang neat-o feature in gnome and compiz, and turn off every feature and effect in windows 7, and odds are, windows 7 will run faster. But will it look nice? probably not. On the other hand, the nice thing about most Linux distributions is that you get options that are unimaginable to a windows user. Like the ability to change out your windows manager in a whim if you are bored with it. Or to change the entire desktop environement. If your only concern is performance, then just about Linux distribution will beat out windows if you are willing to put some effort into it. If you want to just install the disk and be done with it, then Debian wins in this category, but it probably won't be as pretty as Ubuntu or windows 7.

Your question is not a simple one, I guess is what I'm trying to say.

Not so long answer ! Simply use Ubuntu for ur purpose. It is universally known that, almost all virus attacks Windows related flavor and Windows 7 is not excluded that. Debian I not prefer coz, it is little bit of hard to handle. Ubuntu is so user friendly and almost windows like OS.