I like the Mini...but it's M-14 inspired action is not as smooth as an AR; IMO it's just a minor downside as a trade-off to it's utter reliability.
There are match barrels made for them, it would be an interesting project.
I think in the end, for the same dollars spent an AR build would be more accurate. Then again, having a tricked out- and accurate- Mini has always had the "something different" going for it.
I would go with the Tactical... while the harmonic dampener is interesting (I'm not sure what you mean by a "rubber balancer"), I've yet to hear someone report on it. I can't help but think if they were effective, everyone would have one.