I think it would be very interesting if there's a MATE (slack)build for Slackware ARM.
If KDE4 works nice with an ARMv7 processor and 1GB RAM, (ignoring hid glorious bug called "Plasma icons unclickable"), there are many ARM devices that have 512MB or even 256MB RAM.
Even I have a netbook that works well and responsive under Slackware ARM, but has (only) 256MB RAM.
So the most comprehensive DE for it, is XFCE. Here MATE has bread to eat, as MATE (aka GNOME 2.x) works well with a small amount of memory, if I remember right...