Who is the best vasectomy reversal clinic in the world?

That would be very subjective. What do you base as being "the best"? Is it the proportion of successful operations relative to number of operations total? If a doctor has done only one operation and it's successful, then he has a 100% success rate. That doesn't make him the best in my book. Is it the most operations done? There's many places that specialize only in reproductive surgeries. They may have many doctors doing just reversal surgery. Again, that doesn't mean that they are the best, although they'd rate high in my book. Personally, I'd look for a place that does reversal on a daily basis and has a relatively high success rate. I'd look for a microsurgeon and one that's not too young nor too old. I'd want to talk with past patients of his; I'd want to hear testimonials. I'd study to see if how they did the surgery, under general or local, in a hospital setting or clinic, with drains or not, what size of suture thread (a few even use "super glue") and whether they performed a two or one layer when reconnecting each tube, what post-operative care they provided. All would factor into my decision.