Barrier distributions derived from fusion and back-angle quasielastic scattering excitation functions are important tools in understanding the reaction mechanisms in nucleus-nucleus collision at near-barrier energies. The excitation functions for the quasielastic scattering of ⁷Li from the medium-mass target ⁶⁴Ni are measured at the angles 150◦ and 170◦ for the energy range of 12 to 24 MeV. The corresponding quasielastic barrier distribution function for this system is derived. The extracted barrier distribution is then compared with the previously measured fusion barrier distribution for the same system to look for any shift in the peak location to below-barrier energy as observed for the ⁶Li+⁶⁴Ni system. Further, the barrier distributions of the system ⁷Li+⁶⁴Ni from complementary measurements of the fusion and back-angle excitation functions are compared with the barrier distribution functions of ⁶Li+⁶⁴Ni. While ⁶Li behaves like a weakly bound projectile, another stable isotope of Li, ⁷Li, behaves more like a strongly bound projectile in collision with the same medium-mass target ⁶⁴Ni.