Core tuff is unidirectional laminate glass.
Uniweft ids unidirectional glass, but has a cross latch of glass within (imagine a netting impregneted within). This cross directional glass should help with stability, but if used in overlays it will show through and does not look all that great.
Thus use core-tuff for overlays and stripes and uniweft in a limb core if you need cross directional support.
I use stablecore quite a bit (similar to uniweft, but it is carbon and only .016 thick.