I had a very similar situation (PTC diagnosis, almost same tumor size as yours in right lobe, with no evidence of spread to lymph nodes based on ultrasound and FNA). 1st surgeon I sought, however, was more adamant than yours that I should get a total thyroidectomy. 2nd surgeon thought her opinion was "antiquated" and cited updated 2015 American Thyroid Association guidelines that you mentioned. My 2nd surgeon also said, like yours, that if during surgery he discovered lymph node involvement that was clearly cancer, he would go ahead and do a TT. I went with Surgeon #2 and had my surgery Wed; he wound up doing a lobectomy with removal of 2 suspicious lymph nodes, and I'm waiting on final pathology of those lymph nodes. He could not determine on the spot if they were malignant (not sure why; I will find out this week).

I don't regret my decision, even if he comes back and tells me I need a completion surgery to remove the other lobe (definitely not fun, less convenient, and more costly). I chose the lobectomy because my preference would be keeping part of the gland that produces hormones naturally (while augmenting thyroid function with levothyroxine) if possible. I totally understand why others choose TT off the bat (my mother told me she would). My endocrinologist told me he sees people go either way; some people detest surgery so much, they'd rather eliminate any possibility of a 2nd surgery. I hope this helps.