I was one who had problems (liver issues) with methimazole, so I had to choose RAI or surgery after being on methimazole for 7 weeks. I chose surgery for various reasons. I have 4 children, one of which is a breastfeeding infant & I wanted to continue nursing. I didn't want to be away from my family and I didn't want to wait out RAI and see what happened. I just wanted it done and over with- I guess, in part, it's my personality. I really think it depends on the individual, your personality, what your “gut” tells you, what your doctor is willing to let you do (if your a good candidate for surgery- stable thyroid levels, over all generally healthy, access to a good surgeon who does a lot of thyroidectomies).
I understand where you're coming from; I chose surgery based on a lot of the same concerns you have. But, RAI works very well for many people I think, just like surgery works really well for others. Admittedly, if I had a family history of cancer, I would steer clear of RAI. Because I was breastfeeding, the nuclear doctor did tell me if I got RAI while my breasts were lactating (I would have had to wean and dry up and then wait an additional 4-6 months to be safe & then they'd send a tracer to make sure my breast tissue wasn't taking up any iodine), there was a chance of getting breast cancer from the RAI in my specific situation, but they couldn't give me a percentage. I just wasn't comfortable with it, but I think for a lot of people, it's probably pretty safe.
Whether you have RAI or surgery, you'll be at the doctor changing meds. every 2 months until the hormone replacement is figured out. I was fortunate- I started on 100 mcg of Synthroid day 2 after surgery. Had my labs 6 weeks later, was upped to 112 mcg. and then another lab 2 weeks, then 4 weeks later. 112 mcg. seems to be the right dose. Everything is in a good place range wise. I don't feel 100% myself (ie- pre Graves), but I feel much, much better than when I was hyper! So, I'm hoping the headaches that come and go and the sporadic insomnia will go away too at some point. I'm hopeful bc even though I had 2 bad nights of sleep, three nights ago, I slept NINE hours straight !!!!! Woo hoo! So, it is possible! Well, I hope you are able to make the right choice for you. Once you're confident and your doctor gives you the okay with your choice, move forward and don't look back! Know that it takes a lot of time though and patience. I'm almost 4 mo. post TT and I'm still trying to find the consistency in feel good- but, it is better & I'm hoping I'll continue on that path!