OC500LEs will cost less as the mass of the vehicle will be less
when shipped (assuming the body is built locally), even if the body
is not built by a local bodybuilder, the cost of the brand "Citaro"
will not be there, Mercedes Benz spent quite alot of money
investing into "Citaro" and thus that cost will be spread across
all "Citaro" buses they sold.
I have to agree with u that most operators will choose the cheaper
OM906hLA engine for the Citaro, BUT do take note that Citaro
IS EuroIV (the new ones are EuroV) complient because of its native
BlueTec engine addictives, and that the OC500LEs with
OM457hLA/OM906hLA are not Euro IV compliant (they are only Euro
III, Transperth uses CNG thus their vehicle runs on Euro IV unlike
their diesel counterparts).