That depends, for most people: anything not Hard that's over 0.70mm (bg 65, bg70, etc) For me: I tried exbolt 63 at 13kg (28 lbs) half a year ago, was nice, but after a month the feeling started to drop a lot. It still won't break! I break one of my rackets with Areobite every month.
I don't really break strings that are like 0.63 or less but my vote goes for BG-65 / BG-3 / factory strings for being a tank in durability. People had those on for years. But for playability and extreme durability those 0.69 strings have my vote and would be my choice, Zymax 69 / VS-69 / NBG95. BG70p would be on my list as well, but too bad its discontinued ;c
