In my personal view, Tysabri is a better drug than Ocrevus (trade name for Ocrelizumab).
If you look at https://www.mstrust.org.uk/about-ms/ms-treatments/ms-decisions-aid you can compare the two drugs. Ocrevus has an average 50% relapse reduction rate in RRMS while Tysabri has an average 70% relapse reduction rate.
Yes, there is the possibility that you could develop PML, but only after 2 years on Tysabri, and then only if you are JCV positive.
Both drugs have the possibility of side effects apart from PML. But in general, most people don’t have terrible side effects on Tysabri. And you are carefully monitored on both drugs, so side effects would be picked up fairly quickly.
Why not wait until you get the results of the JCV test and make a decision then? The scientists have made further advances with JCV testing, so they can isolate people who are more and less likely to develop PML.
(By the way, I started on Tysabri about 5 years ago. I was unlucky and did have side effects - elevated liver function tests - but I still think it’s a good drug!)
Best of luck making your choice of drug. Don’t forget, if something doesn’t suit you, you should be able to change to a different drug. Ask your neurologist or MS nurse for their opinions and also ask your family and / or friends to look at both drugs and see what they think.