In Austria anything up to 6mm2 is usually solid, 10mm2 and up is stranded. Smaller stranded wire is only used for flexes. 6mm2 solid is already quite nasty to work with, but for hooking up stranded wire to Diazed fuse elements special crimp connectors are required (you can't wrap a 10mm2 stranded wire around a terminal screw, impossible) so if you don't have the crimp tool solid is your choice. There you just need solid pliers!
