Hi Lnx!
I am sure people with far more experience and smarts than me will come along and give you a lot of detailed info, but I have a bit of relevant experience, and thought I'd chime in, hope you don't mind!

I spent a lot of time trying different distros and desktop environments (actually, still messing about with some), including Mint MATE and Cinnamon, and I finally settled on Xfce. I love it's clean, simple, design, and all the option for configuring it. I even found some icons to download, was great. However, I returned to MATE in the end. The reason was the extra capabilities in the file manager (Caja/Nautilus) versus the one in Xfce (Thunar). In the MATE file manager, you can open tabs instead of having multiple directory windows open to move files, and there are a few other options that Thunar doesn't offer. I haven't checked out the file manager in Cinnamon, but I think it is Nautilus (is moving to a modified Nautilus, like MATE has), so you would have the same capabilities. So, that's something you would gain in Cinnamon. Whether that is something you'd use is another question.
One thing I found I lost in Cinnamon relative to Xfce or MATE was configuration options, especially easy ones. I honestly was never really able to figure out how to make Cinnamon look the way I wanted. Maybe it's too new to have the themes there, or maybe I just am too dense, but it was really easy in Xfce and MATE, not so much on Cinnamon. One other thing you might loose is the fancy compositiing, if you use that in Xfce. Cinnamon does seem to have that, but again I was never able to get the effects I easily found in Xfce (I didn't use them, but were fun to turn on occasionally!).
The final thing is that Xfce supposedly is a lighter system, and takes fewer resources, both disk space and memory. I don't know about disk space, but when I had all the things running in Xfce that I do in MATE, it didn't seem to take that much less. The thing is, other than the window manager, and perhaps the DE, the Mint version of Xfce is fairly GNOME-y, it seems to me. The apps loaded are much heavier than those in a classic Xfce environment, and use a lot of GNOME programs. So, unless you have a really small hard drive, and not much memory, and a really slow processor, I'm not sure if you will see any performance differences. Hopefully someone who knows more will address this, as I am curious too!
Good luck with your decision!
caerolle
