I have two Leupold scopes, a Vari X II 6x18 with an extremely tiny dot and a Vari X III 8x25 with a Premier Reticle and a much larger dot. I am looking at purchasing a Vari X III that has been boosted by Premier to 18x40 with a 1/2 minute dot reticle. Would that be comparable with the Premier reticle I already have? I don't like the tiny dot as it's hard to see and I use the scope to shoot silhouette.

Any information would be greatly appreciated.

I would expect that "half minute dot" to mean the dot covers half a minute of angle, or 1.047/2 inches, at 100 yards, 1.047" at 200 yards, and so forth.

But let someone far wiser than I am chime in. They may give a completely different answer, and may very well say I am completely out in left field.

Doubless is correct. A "half minute dot" subtends about a half an inch at 100 yards. This is relatively fine (a "target dot"), whereas the "hunting" dots are typically more on the order of a full minute and sometimes larger.