Which is better for a 15 months old baby, simultaneous or sequential cochlear implant?

Hello doctor,

My niece is 15 months old, and we found that she was not reacting to sound. So, we consulted a doctor, who confirmed in the report that she has profound hearing loss in both ears. The doctor suggested cochlear implant, and we decided that we will go for the cochlear implant. But, the problem is that the doctor is telling us to go for a bilateral implant, and we want to go for a single implant. We are worried about the pain the baby will go through after the implant. The other thing is, there will be a scar behind the ear, but I have read that there will be no gnarly scar. The clinic that we used to visit has not given anyone two cochlear implants, all the patients had sequential cochlear implantation. Everyone suggests that there is no need to go for bilateral, as a single implant gives better results. Apart from all this, my niece weighs only 6.7 kg, which is very less according to the pediatrician. Will she be able to recover after the bilateral implant? Her hemoglobin is 10.7 g/dL. Which is better, simultaneous or sequential cochlear implantation?