I have done the ITEC sports massage course, and it was a good one, but on my physio degree, we don't really get a lot of massage (a half day over 3 years), so it was a good thing to do. I don't know about sports therapy as I don't know how many days of massage training you do. Think it possibly boils down to how confident you feel with massage. One thing that might be worth considering is that once you have done the level 3 you can go onto doing the level 5 advanced course which might be of use in securing a job. Don't sports therapists tend to be self employed largely anyway? It's not a field that I think I have ever seen a job description for.