The Commissioned Corps application board will look at your CV, GPA, and references. They are considering new graduates as well as those with experience, so as long as your overall application packet looks good (decent GPA, good references, a well-polished CV) , only having 1 year of experience isn't an issue. There is also a phone interview in which they will ask you some typical job interview type questions, with some emphasis on what motivates you to serve in a uniformed service. In fact, if you are too experienced (i.e. over the age of 44), you wouldn't qualify for a commission anyway, so being young (and healthy) is generally an advantage. What it mainly comes down to, though, is whether you are willing to work at either IHS, BOP, or FDA-ORA (Indian Health Service, Bureau of Prisons, or FDA Office of Regulatory Affairs). They will ask you this during the initial application process, and you basically have to give your word that you will apply and accept a job with one of those agencies. To clarify, you have to apply for jobs in these agencies IN ADDITION to applying for a commission with the USPHS Commissioned Corps, since the Commissioned Corps doesn't have the authority to simply place you where ever the needs of the service are. Therefore, they will only move forward with your application if you agree to apply and accept jobs in one of those three agencies.
The advantage of applying to jobs in these agencies as a PHS commissioned officer as opposed to a civil servant is the different pay rate and benefits you get as an officer, as well as the additional responsibilities and opportunities you'll have in advancing public health. As a PHS officer, you have opportunities to go on domestic and international deployments in response to public health emergencies (e.g. man-made or natural disasters), you also have increased mobility among the various agencies that make up the Department of Health and Human Services as well as other agencies that PHS has memorandum of understandings with (such as the Department of Defense, Department of Homeland Security, and others), which enables you to have a unique and varied career. Also, if you have an interest in serving in the Coast Guard as a pharmacist, you must be commissioned as a PHS officer first. Lastly, you get to serve your country and provide care to some of our most vulnerable citizens, and you get to wear a distinguished uniform while you do it! If any of those things appeal to you, I would encourage you to go ahead and apply - you won't know what your actual chances are until you try.