Hello!
If you are confident in your application, I'd submit them if they're ready - the quality of your application holds more weight than the time you submit it! Even with rolling deadlines, a lot of firms often keep reviewing applications up until the deadline, and it's not unusual for candidates to be progressed even when it's later in the application window.
That said, if you feel your application could be stronger with more time, there's no harm in holding off and aiming for the spring schemes. The two processes are usually treated separately, so most firms won't automatically roll you over - you would typically need to apply to that one. However, last cycle, I did apply for a WVS (at a different firm) and whilst I got a rejection for that scheme, they offered to roll my application over to the SVS as it was considered strong. I'm not sure how common this is across firms, but it can happen sometimes!
In short - apply now if you are happy with what you have written, but I wouldn't stress if you feel it is better to wait and give yourself a better shot in spring. I hope that helps, and best of luck with your application!
