Referring to a post in AWS on difference between AWS i2 instance and i3, it is essentially using Amazon Linux AMI on Intel E5-2686 v4 (Broadwell) processor, so what exactly makes difference in performance between i2 and i3 instances, provided same specs?
From Previous Generation Instances:
Compared to I2 instances, I3 instances have over 4x higher I/O performance, over 2x higher disk throughput and 18% more SSD per CPU. I3 instances offer Non-Volatile Memory Express (NVMe) based SSDs offering lower disk latencies than I2. I3 offers the lowest price per read IOPS of all EC2 instances.