To me, there are some pretty big differences between the two. The Halo Pearl is a very strong pearl. It sort of reminds me of the No Rules Pearl in that it has the teeth to handle a pretty decent volume of oil, especially for a pearl. The AstroPhysix, on the other hand, seems to be best suited for medium volumes and excels when you need to get in and wheel on it.
In my world, you could very easily carry both of these in the same bag. On the THS, I think you'd be fine with either one right out of the gate as long as the volume isn't extremely heavy or bone dry. The Halo Pearl would be my choice if they were tighter, and the AstroPhysix would get the nod if they were on the medium to lighter side. Now, for Sport, I would knock the shine off of the Halo Pearl as polished pearls get awfully squirrely when they see friction, which could lead to over/under and designer leaves. However, if you put some grit to it, you may be able to tone it down and use it out of the gate on fresh mediums. In my hands, the Astro would only be good on Sport once the pattern opens up and you need to get in and hammer on it.
Obviously, this is all based on bowler, layout, surface prep, etc., but that's how I'd compare the two and when and where I'd see them used best.
