Nvidia cards follow a thumb rule . 1st digit is the generation , 2nd digit is for the model variant. 3rd digit is for variation.
if you increment generation by 1 then , performance exceeds for a single decrement over the model . ie a 860 better than 950 , 880 better than 970. if you increment generation by 2 , the performance exceeds for the a single decrement over the previous model ie. 960 outperforms 770, 970 outperforms 780.
So yes an 860 is better than a 950. Although the perfromance difference is not really noticeable and similar fps can be attained at same resolution with a few settings lowered.
I would suggest to go for the better deal one and also the one with better build quality. A newer launched model is usually more...