High-performance strained Silicon-On-Insulator (sSOI) nanowire (NW) transistors with gate length and NW width down to 15 nm are reported. We demonstrate sSOI π-Gate n-FET NWs with ION current of 1410 μA/μm (when IOFF = 70 nA/μm) at VDD=0.9V and a good electrostatic immunity (DIBL = 140 mV/V, SSSAT = 76 mV/dec). Effectiveness of sSOI substrates for n-FETs is shown with an ION improvement up to +40% at short gate lengths. More generally, size- and orientation-dependent strain impact on electron and hole transport in long and short channel π-Gate (s)SOI NW transistors is systematically studied.