> I'm looking for something easy to tweak

KDE probably. GNOME is more dogmatic about how you should be using it, so fewer tweaks, fewer extensions, etc.

> good switching between "desktops, "

Both can do this without issue. And it's really central to GNOME's paradigm (instead of alt-tabbijg, they want you to basically have one application per 'workspace'—I think that's what they call it).

> is reliable, and as lightweight as possible in regards to memory usage since

I think that GNOME was generally considered lighter than KDE, but I've seen recent anecdotes that is now flipped in KDE's favor.

I'm using KDE, and for what it's worth, you can configure it to fairly closely resemble and function like GNOME.