To understand the long term value of maintaining a certain reputation would require a careful evaluation of many details like how many long term clients and one shot buyers the company has? What could be the cost of loosing faithful clients? Can some more aggressive marketing bring enough new clients over time? There are strategic decisions involved here.
If a sales campaign changes the image of the company, what kind of clients would it be targeting, are there enough people with sufficient spending power to become clients in that segment of population? This is another strategic decision.
Probably the two departments already gathered some data and made their studies, but if they have no clear numbers on what ground are they pushing their ideas? The conflict rather than about creativity seems to be about strategy and if they can't agree the only option is to involve higher level managers, but before both of them should put down their opinions in clear numbers.