For just about everywhere I've worked, the DBA takes the senior role.
That's because to be a half decent DBA, you need to understand development (to make sure you're doing the design correctly), the network (you want to keep your database server running nicely on the net, yes?) and a good degree of systems admin (tune the database to processors, drive arrays, memory usage etc.), along with security awareness for the system as a whole, not just the developed code (keep abreast of latest worms, set traces for invalid access attempts etc).
Inside the corporation, the 'seniority' is, as always, determined by Management. In the general IT community, a decent DBA is awarded more respect than a pure developer (well, that's my experience anyhow).
There again, one of the responsibilities of 'seniority' is using the extra weight of the voice to get the concerns of those more junior roles to get their voices heard where necessary (and explain to those that don't understand, the error of their ways). When all's taken care of properly, there's not usually a problem with Developers Vs DBA.