Halo is very slick. Gets almost glassy when it's tight and starts to see some use. Kinda like mono but without the spontaneous breaking lol.
That said, it can also slip around on the string if it isn't tight and doesn't double serve well. It also doesn't melt smooth if you like to burn a blob on the end for finishing or whatever. But I use it a lot, and like it.
62XS is my go to for double serving a skinny string, and it's great as an all around serving. Not quite as slick as Halo, but grips the string well and is in general a dream to work with. Wears well too.
Email Chad Weaver to get whichever you choose, he will fix you up cheaper than anyone.