The 70 year old- as he is still one generation closer to the past and his DNA would be closer to someone one more generation back..make sure the DNA is
direct Butler males. Butler male to Butler male.

I have a 92 year old Butler cousin and another 65yr male Butler. The lines are twin brother-but mine is from the youngest male produced by one and the other cousin- even tho it's the same line-is from eldest child of the twin- there are 3-4 generations apart..The 92 year old is better choice. Closer to my GGGF than cousin is.