Jake, you've posted a fair question that deserves a good answer, so I'll give it a go.
Actually wieght is a consideration. Wear, steel agianst steel would not be good either. There needs to be some for of bushing to extend the life of the bearing, in this case, the bearing is the hole in the bellcrank.
It also depends on what you are using for leadouts. Steel cable, or wire.
Back when all that were available, were perfect, or Fox brand bellcranks, no one who was serious about flying would have used them without drilling and installing a brass or copper bushing. This was most often done by first drilling a 1/8" dia. hole where the leadout was going to connect, then, cutting a short legnth of tubing, 1/8 OD that could be soldered with a washer top and bottom. We took care that these assemblies could freely move once installed.
After that, it didn't matter whether we used cables or wire for the leadouts, as the bushings took the wear.
With the plastic bellcranks such as the Brodak or Sigs unit, the plastic is a good enough bearing for music wire leadouts. Cables on the other hand, if left unbushed, will rapidly wear through.
Bushing these types of bellcranks is pure simplicity once you've done one. First, drill a 1/8" dia. hole at the points you want the leadouts to attach. Then, with a drill press and an oversized drill bit, just touch the newly drilled hole on both sides, top and bottom of both of the new holes. Just enough to put a chamfer on each side.
Now, to bush the hole you will cut two pieces of brass tubing, about 1/16" I.D. about 3 to 3.5" long. Next, slide the leadout cable through the brass bushings, leaving about 3 or more inches of the leadout cable protruding from one end.
In the middle of each of these brass bushings with the wire through them, use a 1/4" to 3/8" dia. dowel as a guide and form, and bend them 180 degrees. they will now look like an elongated U on it's side. If you didn't have the cable already through the bushings, you won't get it through there now, so make sure the cable is in place and that you have enough sticking out the other end to make your wrap before you bend the bushing.
On both sides of the U, about 1/2" to 3/4" from the bend, bend the tubing on each leg twice more. First towards the center, and then back out. The goal is to have both sides of the U parallel and adjacent to each other.
Now, slip the prepared ends with the bushing on them through the chamfered holes you previously drilled. bring the two parallel legs together and do your wrap. I make the other end up similarly for the other end later when the plane is covered and finished, preferring this type over the little round eyelets.
I also finish off with a short legnth of heat shrink tubing that was slipped a short distance onto the two parallel legs before being shrunk.
This makes for a light, bullet proof plastic bellcrank/cable leadout installation.
In use, Over years of flying, I've never had one prepared this way, wear out or fail. I have had problems with connections to the flap horns and elevator horns, but so far, the ball links I now use, show no wear.
Carbon fiber cranks could and, in my opinion, should be set up the same way. These new horns are stronger than steel and are considerably lighter.
Going to steel bellcranks will not add significantly to the longevity of the control system, compared to aluminum or plastic units correctly installed, but they very well could add enough extra weight to make me reconsider.
I know we stunt types are always obsessing about weight wearas the sport flyer figures to over build to allow the plane some margin, in the builders mind anyway, of safety or survivability.
There are two mindsets operating here that are at odds with each other. Build light and have an easier flying plane, or build to survive. Light planes fly better and a skilled pilot can often avoid a problem. There's also less mass in motion so depending on the type of mishap, should it be unavoidable, we have less energy to tear the plane apart when it does contact the ground in a less than perfect landing.
Build strong, (heavy) and you'l surely be testing out the plane's survivability. So we who do fly competition often prefer to count the grams and ounces.
I realize, that you are probably aware of preparing your leadouts in this manner and perhaps even have a better idea, but we have enough newcommers and lurkers who may not and hope that this explanation wil help them avoid problems alng the way.