Yes, MRI guided is supposed to be better but other radiation oncologist have said that CT guided is just as accurate, Of course that’s what they use.

From 2024 conference

MRI guided radiotherapy is a promising new technique and may reduce the risk of certain side effects of prostate radiotherapy (urinary, bowel, sexual) within the first 2 years after treatment
• MRI guided radiotherapy still needs further study, the MIRAGE trial was a small clinical trial done at a single center
• It remains unclear whether it is the technology (MRI-Linac) or the smaller volume around the prostate that was treated in MIRAGE which results in fewer side effects

If you are really concerned about the side effects from radiation, then you should take a look at proton radiation.

Proton radiation therapy definitely causes less secondary cancers than other radiation therapies. They prefer to use it in children to avoid secondary cancer risk over their lifetime. Proton therapy machines have been extremely expensive to build or treat patients, which is why it is so much more expensive and less used. They have finally been able to get a proton machine built in one and two rooms, which will greatly reduce the expense. Eventually, it seems proton, will probably be equal in priced to other techniques and will be used much more often.