i've read about the differences b/t the two certifications..and perhaps i'm basically answering my own question, but here goes:
i have two bachelors degrees (psychology & neuroscience--basically a biology degree with neuropsych/neurobiology courses thrown in), and the ACSM said that i'm technically qualified to apply for the HFS certification.

I prefer to apply for the HFS cert b/c it builds off my education to an extent, seems to give you more career options, and I see that ACSM refers to the HFS and the 'advanced certified personal trainer degree'....

i basically want to make sure that the HFS isn't "TOO" specialized. I plan to apply to local gyms after becoming certified, but also plan to take it to the next step in the near future and apply to hospitals/universities. I just want to make sure the HFS certification wouldn't preclude me from getting a job at a local gym. I noticed the HFS study kit doesnt include the CPT book that the ACSM CPT kit includes. are the two courses of study that different? or is the HFS exam basically a more indepth and 'extended' version of the CPT exam w/ more emphasis on working with patients w/ specific health conditions ?