Hello.
I have decided that I want to switch distros, because elementary is getting unsatisfying. This is my first distro,btw. I"m considering switching to Arch, but I don't know if it's faster than Debian. I need advice.

Given a similar setup (same DE, etc.) arch can be faster If you do a lot of stuffing around. But not by much. IMO anyway.

Debian is a lot easier to use for a ubuntu refugee than arch.

You might do better to use slackware than arch, IMO rolling release distros (like arch) are a little to prone to breakage.

as far as i know you can compile packages on arch so that would speed up your computer a little. However there are ready made arch distros like Archbang.

It would help if we knew what was "unsatifying". But since you say your computer is low-powered, I assume that it's struggling a bit with Gnome?

If you're used to Elementary, then it would make more sense to stay in the Debian family. You could try Mint. which seems the best of the bunch to me. Try the Mate version, and if that doesn't improve things, then the Xfce one.

Arch does things very differently: there's the right way, the wrong way, and the Arch way! But the documentation is very good. The genuine article is tricky to set up, as there's no installer: just a set of commands you enter in a console. Bridge Linux is an installation disk that sets up Arch for you with Xfce.

Given the exact same configuration (same DE, same daemons running in the background, ...) there should not be a significant difference between those two (or any other) distros. Arch should be slightly faster, but that should be unnoticeable. You will get the best speed improvement by choosing a different, more lightweight, desktop environment, like MATE, XFCE or LXDE instead of concentrating which distro to use.

In elementaryOS you can do

same for LXDE, MATE. I would throw in Fluxbox and Icewm also but it might be more than you can handle.
Judging by your query.
How I can make Icewm look for me http://antix.freeforums.org/download/file.php?id=556

So, if I got Cinnamon (which is what I use now) on Arch, would it be faster? And is Debian any faster than elementary?

Given the same configuration, in both cases: No, not noticeable.