i've used both durability: both equal however, zm70 (without prestretch) tension retention much much better, so it's more playable for a longer time whereas bg65 (if not prestretched) would lose 2-3 lbs after 1-2 months!
equal, I use both regularly. under ideal conditions (no mishits or bad grommets), both last exactly 6 weeks for me.
since his original post indicates that he cares about durability, zm62 might not be the most fitting suggestion. zm62 can break in days. zm67 is much better but still no in the league as ZM70 or BG65.
Thanks for all your replies I play feather This was just for a friend of mine who's looking for a durability string I use the 0.62-0.66 stuff I don't mind stringing, its kinda fun