I have no direct experience with Stringjoy, but hear decent things from those who do. I have long used Elixir Nano PB but a recent test of D'Addario XS has been very favorable on one guitar. After two months they are holding up very well. My normal go-to strings are D'Addario EJ16 PB, Elixir Nano PB. and GHS White Bronze (nickel alloy). Some guitars prefer one type over the other, and experimenting is the only way to learn.