The switchlug is pinned and doesn't rotate. The Barloc puts preload on the threads.
I've never used the switchlug so I can't comment on RTZ. By drilling into the receiver face, you are weakening it in an area that is under stress during firing. That said, there's lots of pinned lugs and receivers out there that are doing fine. Cutting into a safety factor, up to you on the risk v. reward thing...
The Barloc can shift up to maybe a half mil in any given direction taking the same barrel off and replacing it, IME. Most of the time it's not that extreme but it's worth 3-5 rounds to re-check zero if you ask me. The Barloc can spin around freely until it's tightened down and I think that's what contributes to some of the POI shift. That said, I fired a composite group ranging from finger tight to the full torque spec on the Barloc screw and POI did not shift substantially through the torque range. YMMV. Also, doesn't require sending your receiver off to get machined. Depending on the action people like PVA are making prefits for it and it's compatible with most savage prefit barrels.
Internet opinion here; I think the Switchlug might give better RTZ and might be a little more user friendly, but I think the Barloc is more resilient, gives more options and maybe better-engineered. Doesn't weaken the action, applies thread preload, shouldered AND prefit barrels, at the cost of having to align it (for looks, really... functionally it will work in any orientation) and maybe a wider range of RTZ error.
ETA: I don't switch barrels often. Maybe once every few months. For me, though, it's worth it to be able to order prefit barrels and swap them out when the time comes even if I was running 1 caliber at a time until it burned out.
