Tactical vs. USP
I have a MK23, full size USP .45, and a compact USP .45, all of which I would never depart with. I added the match trigger to my Full size and found that it does indeed make a difference in the pull, as well as the travel stop. IMO, it was well worth the cost and effort. I put it in myself and it was fairly straightforward. The only 2 things that were a pain was the trigger and hammer spring.
Accuracy: I find that the Tac is more accurate, as the MK23 is, I would say the O-ring helps. Cost between the 2 is not that bad, $650-$700 for the USP and $850-$950 for the Tac. Add the Match trigger for $100, the Threaded barrel for $300, and the target sights for $150, and you actually exceed the stock price of a Tac.
In regards to the comment of a Grand Jury caring about a match trigger, I do not agree. The circumstances involved in the shooting will be the primary focus. If the comment was intended to imply that a round could be fired accidentally, I place that responsibility on the shoulders on the shooter. Call me crazy, you gotta pull the trigger to fire the weapon.
Just my 2 cents.