I faced a very similar decision a few years ago, and quickly realised that I looked much better in green than in light blue. I'm still firmly of the opinion that RAF tropical dress is the finest order of dress for ladies, so I think that should have a bearing on where you decide to go.
More seriously, my impression is that the RAF is a more "modern" organisation that the Army. As you develop into your career, the RAF will concentrate more on management, whilst the Army is more focused on leadership. I think you do need to be slightly more robust in the Army, physically and mentally. So really it depends entirely on what you want, and how you fancy living.
Also, most field hospitals on operations nowadays are tri-service, so no matter which service you join, you will almost certainly end up doing the same job in the same location.