What would be the most efficient version of Ubuntu to install that would outperform Windows XP in speed and overall efficiency?

What would be the leanest, most efficient version of Ubuntu to install (dual boot) on my Acer Aspire 1.6 AMD Turion with 1gb ddr2 memory) that would outperform it's dual boot companion, Windows XP in speed and overall efficiency? I thank you in advance for your anticipated assistance and cooperation with this request.