I started Cowboy Action Shooting about a year ago. We use lever action rifles in pistol calibers and the .357 (shooting .38 special usually) is the most popular caliber. In my local club a monthly match is about 60 rifle rounds and 60 pistol rounds which is pretty typical. Lots of cowboy shooters go to more than one club each month. Factor in a little practice on top of that and do the math; cowboys put a lot of lead downrange. The membership numbers in SASS (Single Action Shooting Society) has topped 90,000. The cowboys can tell you from experience what guns work, over the long haul with "high mileage". The game is about speed, so guns that run rough, or break down, don't make it.
Several years ago the Marlin was highly favored, in part because the lever stroke was a little shorter than the Winchester '66 and '73 (which employ the same toggle action) and the Winchester '92. The shorter stroke gave the Marlin a speed advantage.
Later on the tinkerers figured out a way to change the angles on the links in the '66/'73 models and create "short stroke" kits that made the lever stroke shorter than the Marlin's. Coupled with the simple mechanics of the old Winchester design, the "short stroked" '73 is now the most coveted lever rifle in CAS. They are also darned expensive, almost twice the cost of a stock Marlin.
I've used the Marlin rifle a number of times and at my skill (speed) level it is probably more than adequate. On the other hand, I really like the style of the '73 and I saved up for the difference.
The '92 is a nice rifle IF well made. Some of the modern guns (except for the Marlin most of the cowboy guns are reproductions, most imported) are pretty rough but can be improved (insert dollar signs here). The '92 (invented by John M. Browning, donchaknow) mates a stronger locking mechanism with a more compact frame than the venerable '73 (dubbed "the Gun That Won the West"). If you want to shoot full power magnum ammo, the '92 is probably better than the older designs.
The '92's strengths, though, are not needed in CAS since the rules mandate ammo with lead bullets at low to medium velocities for safety's sake (we shoot steel targets at relatively short range). The '92 will not run as fast as the toggle guns or the Marlins, so they are less favored by the Cowboys.
OK, some caveats, retractions and apologies. There are thousands and thousands of '92s in use in CAS. They can be made to run pretty well (Google "Nate Kiowa Jones" to see what can be done to improve ($) a '92). John Wayne used a '92 in the movies (even those set before 1892) and the Cowboys say, "the Duke can do no wrong".
The Henry Big Boy? You don't see many of them at CAS matches, even though SASS made a rule change to allow use of the "modern" Henry, which isn't a reproduction of anything, not even the original Henry, although both have front loading tube magazines.
One drawback of the front loading Big Boy in SASS has to do with our system of running dozens or hundreds of shooters through live fire matches without putting unwanted holes in one another. We have a "loading table" where the shooter comes to load his shooting irons. After you finish shooting the stage, you go to an unloading table where someone supervises you unloading to confirm your guns are clear. Both tables are oriented so that your guns are pointed at a berm (in a safe direction) when laid on the table.
When you are loading a Marlin, for example, you can lay the rifle on the loading table, pointed at the berm, and leave it there while you stuff cartridges in the side loading gate. Very safe and under control.
To load a Henry Big Boy, you have to stand the gun up vertically (or nearly so) to pull out the magazine tube from the front and drop the cartridges down, then manipulate the tube back into place. Not quite as "foolproof" as loading a rifle laying on its side pointing downrange.
If you like the lever guns, I'd suggest you visit a local Cowboy match and see them in action before you buy. You can talk to the shooters and see lots of different types of rifles side by side. There's a good chance someone will invite to you try shooting a stage, but beware. It's habit forming.
You can find a local club at
http://www.sassnet.com/clubs/index.php