Prelim And Categorical??!

So I've just been advised from my career guidance to apply to prelim positions (I'm going for one of those specialities that needs a pre-lim year) as well as a categorical year in medicine just in case I'm not able to get my desired specialty. What sounds even more confusing to me, is that I will therefore be applying to the same hospital's pre-lim program as well as their categorical program, and will be interviewed for both on the same day. Any one have any thoughts on this? Is this a good idea? I feel that PDs are less like to take me for EITHER just because I'm applying for both. Need advice from anyone who's done this before!
Thanks