Radioactive Iodine Therapy - Hypertheroid

[Okami]

Hello,
I've been having blood tests done on my cat on a yearly basis for the last 4 years (He's 11 years old now). The last year his blood work showed that his Thyroid was a bit high but not too bad. This year his Thyroid has shown very high and the vet has diagnosed him with Hyperthyroid, and low white blood cell count
They've recommended either
1) a iodine free diet with special food
2) medication (less recommended because of the side effects)

My concerns with a special diet is it seems like it's not really treating the problem rather than mitigating the issue.

And I'd like to avoid medications unless necessary for any side effects.

Now I've been researching around and I see that radioactive iodine treatment seems to be very promising. I'm not a vet though so I'm unsure if this treatment is too overboard for a recent diagnosis.

Do you guys have any experience with Radioactive Iodine Therapy?
Do vets usually offer this as a first solution? Or did you try other treatments first?

Thanks!