If better means which I prefered, then nWo wins hands down. I was into them for a long while.
Austin-McMahon never captivated me. Ever.
If better means influence... then I'd still go with the nWo, first since it came first, and also because Austin-McMahon made Vince believe he (and subsequently the rest of his ilk) could play a central role in storylines with shitloads of facetime over actual wrestlers