You can only really train Dungeoneering in one way, so there's not much of a cost VS cost type thing; if you're DG'ing for DG XP, how can you use the cost/hr efficiency argument? You're leveling Dungeoneering at the same time, so it might as well be said that you're training Dungeoneering as a main objective and gaining tokens on the side. I guess I just find it unfair to negate the importance of the DG XP you get in the examples of FKS VS ASS (lol).
Because dung XP is useless after 85 unless your in it for the e-peen.
Everything after that has tokens as the primary objective. And thus you measure the efficiency of gaining tokens in comparison to gaining money.
You don't DG to unlock new content? That's my main objective...
The DG bosses are more challenging and have better mechanics than RRS bosses (even though some would disagree for the sake of disagreeing...) and the lore keeps up with even the best quest storylines.
I thought of a better allusion to clarify what I said before though - Woodcutting with Ivy or Magic Trees.
Most people consider Ivy more efficient because they can make more money through other activities while gaining quicker XP with Ivy. For Dungeoneering, aside from rather random bits of XP from bonus sources (and no tokens at that), there truly is only one place or method to train it. To simplify the argument: DG XP is invaluable because it is unique to training DG directly.
Also to further my previous comment about Castle Wars and the Chaotic Kiteshield:
Magic Defense does not matter [as much] in Castle Wars, for those who are not going after the flag anyway. I have first hand experience from when I was 95ish Magic that one can easily hit through Armadyl and Deflect Magic and even quite high at that. Even those people with Spectral, Arma top/legs, Inf boots - the works - can often get frozen and then killed with just Magic, although some will almost always slip through.
Clotting is rather literally just getting as many players as possible to pile you for as long as possible to take away from the other team's Defenses. In this sense, the DFS or CKS are superior to the DSS because you don't want to carry any potions (except OVL, pers-pref) around with you. Typically, ancienters will stay within their own base to guard their flag, so you won't have to worry about them anyway. I personally am not concerned with costs of quicker degradation since I'd already be using CR and since CW has no real benefits anyway.