Actuarial Science is a very specific course. If you are not intending to go into Actuarial field, I would generally advise against taking up AS.
On the other hand, financial maths is slightly more diverse, giving you options. You can still get into actuarial field through financial mathematics course, but it will be more difficult.
The course in AS will help you expand your knowledge on external papers etc..
So, the bottom line is, what is your interest... Do you really know what is actuarial science?
If not, https://forum.lowyat.net/topic/1039295 <-- it's a good read.