What is the best option for large size scalp scar due to Hair transplant plant necrosis? (Photos)

It is best to see a doctor in person for an examination for such a difficult case.  The options you were told are very reasonable.

Larger scalp necrosis scar after hair transplant.  For 35 years I have used scalp expansion to remove large amounts of scar as described in our textbook. Anything short of this will give you a sub optimal results. See a very experienced  scalp surgeon who can show you many photos of his work with this procedure. 

It is true that both options exist. However, I believe that from personal experience a hair transplant would be more successful. If a transplant is done, the graft should not be packed too densely and several sessions would be preferred, providing their is adequate donor. 

Firstly, thank you for sharing your photos.  I am very sorry you have had this result after seeking care to improve your hair.  I agree with my colleagues that scalp expansion with balloons (tissue expanders) is probably the fastest and best step.  Best of luck.

I agree about the two surgical options and my first suggestion and option could the tissue expansion then the possible serial excision. Also, it depends of the case but hair transplantation is very successful in several scarring tissue cases but it depends of the tissue and surgeon's training and experience. I have a very good friend of mine with great experience in tissue expansion and hair transplantation in Md.

Another option would be to perform a series of fat cell injections into the scar area.  This can be done every few months once the area has completely healed and matured (typically about a year after the scar tissue sealed).  The fat cells will provide healthier tissue and help the quality of the overlying scar, and improve circulation.  You could then try hair transplantation again, starting slowly and using less density than usual.

plastic surgeon suggested you very well...skin expansion by balloon is a good option..
we had many patients of 3rd degree burn and we did hair transplant with a promising outcome...if you are not willing for expansion than go for hair transplant and it will work out...

The best treatment by far fro this condition and possibly the least expansive is the balloon expander,  See picture and post below. I have had patients who wore a hat to cover the balloon and some hats work well at doing this.