The problem you have is not just which injectable is best, but that if you’re only planning on a 3 month break from Tecfidera, the injectable DMD might not have started to protect against relapses within 3 months.
If you are likely to stay on the injectable however, then your choice is very much a personal one. Side effects are possible from all drugs, so it’s very much an individual thing. Some people experience flu like reactions after injecting with any of the beta interferons, but that can be lessened by taking paracetamol as a preventative. I always used to tell people that Copaxone was a great DMD because it never gave me any side effects at all. But I think I spoke too soon as I’ve recently restarted Copaxone and have really been suffering with injection site reactions. (I suspect my super sensitive skin just doesn’t like the stronger 3 times per week variant, so am trying to switch to the daily version.)
Have a look at https://www.mstrust.org.uk/about-ms/ms-treatments/ms-decisions-aid You can compare all the injectables against each other. I don’t think that any of them have vastly different relapse reduction rates so it’s a matter of what side effects are possible as balanced against the ease of taking the drug (frequency of injections, type of injection, etc).
Best of luck.