Hi shrublemaker, I had the same problem and I created a thread a few weeks back on my second account. I got some very helpful responses and I will break it down for you.
Sport and exercise science is a good course and I found it more interesting because I am a semi-pro footballer who also wanted to desirably work in a football team. I loved the physical side of it and the latest technology used in most universities. I went to Birmingham Uni open day and looked at Sport science and physio, sport science appealed to me much more by far. The problem with sport science is that if you pursue this degree you will be a lost lamb in a massive herd. This is because sport science is seen as 'the easy alternative' to BTEC students (I have nothing against them) and other people. If you do A-level's like me you will be seen as taking the 'harder route' as opposed to BTEC students who can end up on the same course as you.
On the other hand, Physiotherapy is a professional career which guarantee's you a job which sport science does not do. That's another thing I need to mention, sport science is a degree which has low job prospects. There's no way you can appeal to employers compared to other students with the same degree. Physiotherapy is also funded by the NHS which is another appealing measure. Meaning no 60k+ debt and a student bursary of 1k also from the NHS.
So it's up to you. A bit about me: I have chosen to do physiotherapy and I am just about to collect my AS level results in a few days time then go onto a2. I take a levels which are Biology, PE, Psychology and Economics.
Hope this helped.