In a certain way, it is a tossup. The S1 Turbo is speed rated higher, it is spin rated lower. The ratings that the companies list often don't mean much. But with the extra spin from the BF M1 Turbo may be worth it. It is the safer bet in a certain way. But Acuda S1 Turbo may be the faster one.
The way I look at this stuff, if it is a choice between two rubbers, and you try one and are a bit disappointed, then in a month or two, after it has been decently used, you have a chance to try the other one and see if you like it better.
So, why not go for the Acuda S1 Turbo if you feel like you are leaning that way. If you like it, done deal. If you end up feeling you need a bit more spin, then try the BF M1 Turbo after you have worn the Acuda S1 Turbo out.