Impact and don't look back, Tate is about the most straight forward guy in the industry. You'll get what he says you'll get, when he says you'll get it plain and simple. The impact runs smooth as butter and simply flat out works in any conditions which is why so many of the top guys are using them. There's a huge difference in being paid to run an action and running one by choice, I won't mention any names but there's one particular company that's lined shooters pockets for the marketing. Tate at impact will flat out tell you, I don't sponsor shooters with free actions my work speaks for its self, yet many top guys are running them by choice. Tate also has these on the shelf and will at any later date spin up a barrel for you and mail it, many other companies will also due to the consistency of the impact action.
The Curtis stuff is nice but bolt lift is significant over 90 degree stuff, the actions nice but the customer service isn't what is say is good... Timelines tend to shift but the finished product seems nice enough. I think you'll find once behind a nice 90 throw the amazing wow of a 60 isn't all it's cracked up to be.
The arc stuff while maybe nice isnt something I'd even consider because of the lack of customer service and support from Ted, I mean even magazines are out of stock.... Mythical nucleus actions hundreds are waiting on speaks volumes.
The defiance stuff is very nice, however the tolerances tend to be to tight for any real dirty conditions, on more than one occasion I've seen a defiance guy saying how smooth his action is only to be oiling down and cleaning the bolt half way through a match because he's got some grit in the action. Your look at HUGE leads if you can't find what you want exactly in stock, but call Norm he's a very nice guy and will do what he can to help.
The big horn is a rock solid action all around, I can say the mechanical extraction is not for everyone and does require a full bolt stroke. The play in full open tends to make if bind when I run the bolt but many have no issue.
Hope this helped some, flat out I've been behind them all, the impact is a rock solid choice.