By definition, this is a pointless argument. The points costs don't exist in a vacuum. Here is what Games Workshop says is the best use for R.C.
Warriors with repeater crossbows provide a versatile and reliable bastion of fire for a Dark Elf army. They work well in large units were they form a solid line of fire. Neither unit type can move and fire, so be sure to set them up with good lines of sight in mind. Always equip them with shields, the increased save is useful, especially in combat where they get an additional bonus for hand weapon and shield.
Conversely, the use for Chaos Marauders is this:
The men of the north are natural fighters, born into hardship and brought up in a world where only the strong prosper. Every man is expected to be a tough and capable warrior, independent and fierce. Chaos Marauders fight with heavy axe, blade or flail, and their favourite tactic is to charge in great howling mobs towards the foe.
In the official tactica, they also say Marauders provide "much needed bulk" or something along that line.
My contention is Marauders as bulk are pointless since they rely exclusively on static combat resolution bonuses to win fights since they are among the worst fighters available. We have not run a statistical model.
There is a serious problem with any statistical model which is one reason I have not bothered to do one until now. They are based on thousands of events whereas a statistical model assumes every individual roll happens exactly the way they should happen over thousands upon thousands of events. Individual events that go strictly according to percentage are actually the anomaly.
Also, they happen in a vacuum. For example, in the first one I am about to do, I will assume the Dark Elf player is a complete moron who never threatens flank charges or charges with good units that should be protecting their shooters, never moves their Crossbowmen to give them an extra turn or three of shooting with their mobility advantage, and never march blocks.
I will also assume the Chaos player is a moron who intends the Marauders to win a combat and can come up with no better plan than walking straight forward into a line of Repeater crossbows without any precautions such as a mark of Nurgle or Tzeentch.
For this model I will use the smallest possible sample size and will make the following assumptions. If something happens 50% of the time, I will assume the first time it does not happen (IE, if a shot hits 50% of the time, we will assume it misses the first and hits the second). If it happens once in three times, I will assume it hits the second time.
Marauders cost 4 points, Repeater Crossbows 10. So 2 Crossbows versus 5 Marauders is the statistical model.
So we start 24 inches apart and give the first turn to the Marauders. That should give them every possible advantage and they should win this.
Walk forward 8".
Shooting 1: 4 shots:Start needing a 3, over half range, multiple shots, they are needing 5s. One of three hits so we will have 1 try to wound, 50%, no wounds first turn.
Walk to 8". 4 shots needing 4s, 2 hits, this time one wound. 4 Marauders left.
Charge. Stand and shoot kills one more, leaving 3 marauders to face 2 Dark Elfs. I have two shots at passing my panic test so I will auto-pass it. Only about 11% of the time will I fail it so 9 of 10 times I make it into close combat.
3 attacks, needing 50% to hit, 1 hits, have 50% chance to wound, no wounds.Dark Elfs attack back, 50% to hit, 1 hits. Eternal Hatred means re-roll, 50% to hit, to give every possible advantage to the Marauders, we will say it misses.
Dark Elfs have Initiative 5 to 4 for the Marauders. 50% hit, no re-roll this time. This is the second of 2 50%, so one Marauder dies. 2 Marauders left. 50% hit, so one hit, this time I kill a Dark Elf who only saves one in 6 times.
Round 3: Dark Elf attacks first, 50% hit. This is his third attack so he misses. I have 50% to hit, 1 try to wound, wounded last turn so no wounds.
Round 4: Dark Elf hits this time, no wound. I hit once, kill once and win with 2 guys left.
So lets switch the model and make hits/wounds/saves happen on the first event occurrence.
Marauders move to 16".
4 shots, 2 hit. 1 wound. 4 Marauders left.
Marauders move to 8". 4 shots, 2 hit, 1 wound. 3 Marauders left.
Marauders charge, one more dies on the charge, 2 left.
Marauders attack twice, wound once, saved.
Elves attack twice, hit once, re-roll means they hit twice, kill one Marauder. One left, needs to pass break test on a 6 which is 50%.
Dark Elf attack 2 times, hit once, no wound.
Marauder attacks once, hits, no wound. Takes break test on 7.
Dark Elfs attack twice, wound once.
When the advantages are all Marauder, they have 40% of their force left. When they are all Dark Elf, the Elf ends with 100% of his force left. Of course, an easy split of the 16.6667% chance of save means they only get 50% of their force.
As you can see, with dumb players who don't do any maneuvering, march blocking, flanking, or anything of that nature, it comes down to where the model falls. If the breaks go the Marauder way, they are left with a decimated force that gave up 1/2 points. If the breaks go the Dark Elf way they are left with a fully functional force.
So if you run the model each way the Dark Elf player ends with 15 points for the two games to 10 for the Chaos player and if you run the model a third time, now it is 10 crossbows to 2 marauders.
Of course, this is one reason I think these models are often an exercise in futility. More often you will see one game where the Dark Elf player consistently rolls 1 under the score he needs to hit and when he does hit the wounds do not go through and then the next game he will hit 9 of 10 and wound 8 of 9 or something ridiculous like that. I have been on both ends of those things.
Ultimately, it comes down to play style.
Marauders in my armies are only useful as screening units. They need to attack with 4 guys against units with no save to expect to do even a single wound. That means I have no confidence in their ability to do damage so their only real uses are as support for Wulfrik or screening purposes.
For screening, Warhounds are better. Costing 2 points more, they are much faster which allows my Knights/Shaggoths/etc to get into combat faster, though they die just as quick and run much easier.
If Marauders could skirmish they would be worth 6 or 8 points apiece as they are harder to hit, and if they could move and shoot, they would be worth 8 or 10 points apiece. With no range weapon, they are just pointless casualties in my playing style.
Conversely, in my playing style, line troops who can shoot enemies to ribbons as they come across the field and then be just as good as my screening units in close combat, those I could always find a use for.
Long story short; I have a sneaking suspicion both sides of the debate see this model as proving their point. To me, it clearly shows Marauders are over costed in the Chaos army (though possibly under costed in many other armies) and an equal number of Repeater Crossbowmen is a better value while my disputing party will think it shows his point.
As usual with things that entirely hinge on playing style and knowing your own armies weaknesses...their value is completely subjective. One mans waste of points is another mans gold mines.