Many people claim that Linux (e.g. Ubuntu) has a lower memory footprint than Windows. Is this really true? E.g. between Windows 7 and Ubuntu.
As of now, yes, that is true. Windows (at least Vista and 7) tends to use a lot more memory because of a technology called SuperFetch which preloads the RAM with programs that you use frequently or recently. However, this makes programs a lot faster to launch. But on the other hand, Windows has a heck of a lot of graphics (and hence, memory) intensive effects. These effects are all-or-nothing. In Ubuntu, the effects are much more configurable, and are set to "Light" by default.
I'm sure some Free Software purists would argue that the code is a lot lighter because there are so many people looking at it, constantly tweaking it. This point isn't all too valid because a lot of open source projects are bloated too (see: OpenOffice.org, the original Mozilla suite, KDE 4.0).
Furthermore, why does Windows take
considerably longer to boot up than
Canonical works their butt off optimizing boot times. With the upcoming ChromeOS and Ubuntu Light and all that jazz, they need to use boot time as a market point.
In addition, Ubuntu and Linux in general doesn't have a registry, which is the bane of Windows users. The registry is so easily corrupted that you can't go 10 pages on the Internet without seeing a "Registry Fixing Program". Linux programs save their configurations in . in the user profile folder.