@Dan W - would tend to agree with yr assessment. Out here we do a lot more sectors and as such it can be argued as we work much harder we should get paid more. However, as per me it should be on the "same job, same pay" principle. The senior lot can be compensated by recompensing them for their yrs of service.
@Burnable G - if u compare the amount we fly vis-a-vis widebody crew, then the total passengers carried would equate to probably more revenue being generated by narrow body crew. So the "more revenue" argument does not really hold good. At least not here.