Mahindra XUV 500 will be the best in these two as I take a vehicle as the best one with its performance. Mahindra XUV 500 is having the best performance than Toyota Fortuner. Mahindra XUV 500 gives the mileage of 11.5 kmpl in city and 15.1 kmpl on highway while Toyota Fortuner gives the mileage of 7.8 kmpl in city and 11.5 kmpl on highway which is less than XUV 500. source: Mahindra XUV 500 Review
its my opnion that you really can't compare the two directly as they belong to different segments and are very different beasts of burden, while the fortuner has full time 4x4 configuration, the xuv500 w8 model has to do with with awd, if you are the the kind who likes to ferry around his famliy in comfort in city and on the highway, look no further than the xuv..its well equipped, has a torquey engine, and its cheap as compared to the fortuner, if you are the kind who indulges in occassional mud slugging/rough terrain offroading and you are an adventurer at heart, you'll be better off with the fortuner