Sweet, warm and natural sound
I play guitar for a living and since trying a set of the 510L's on my Blueridge BR43 (Martin knockoff) I haven't even bothered with any other set of strings. These in combination with changing out the nut, saddle and bridge pins for TUSQ have made this guitar sound nicer to me than most actual Martins I've played. Has a really warm and inviting tone, like your favourite couch or something.
These have all the best qualities of PB strings but without any of that nasty brash harshness you get before they wear in. They sound smooth, natural and musical straight out of the packet, and they last for ages.
People will often comment these days that my guitar has a sweet or beautiful tone to it, and these strings are definitely a big part of that.