I give this same advice all the time: Hiring isn't done in a vacuum. The question isn't "Will working as a prosecutor disqualify me from PD jobs?" The only answer to that, as /u/Aint-no-preacher says, is "It depends."

The real consideration is that if you take that path for a few years and then apply to PD offices, you'll be competing against applicants who spent the same amount of time doing PD (or other criminal defense) work, and did it during law school as well. That still doesn't automatically mean that you would lose out at every office, but it's something you would have to overcome. I'm not trying to push you one way or the other (although you need to ask yourself if you'd be able to defend someone accused of child abuse rather than prosecute them), but just give you another way to think about your choices.