Both of them are used for hair transplants. The difference is in the process and the result. With FUE the surgeon has to create channels for implantation with a sapphire blade for example. Meanwhile, with DHI the grafts are being implanted directly by Choi pen. Looking at the result for each one, DHI gives a more natural look cause the surgeon has the ability to control the direction of the implant and maintain the hair flow. Or with FUE, the surgeon has no control of the grafts, specially when it comes to frontline it will not give best results
And as you said, it's all related to who is doing the surgery and how experienced he is to give the best results