Both medicines you list have strong safety profiles and stood the test of time (although the Extavia brand is newer, but I believe is is the same as
Betaseron), as have a few other medicines you don’t list. And you can always change your mind later, although you should give a drug at least a few months to work. And yes, there’s a chance it might not work out for you, but MS progression definitely won’t work out for you, and so you are right to try to attack your MS with something.