Best can be, better than what else you race or run against ...
Can be what builder gives the best after purchase support ...
Or can be what builder holds the most records or documented success with there branded engines ...
Many VERY good tuners currently, a few turds as well. Best tool you have in determining who has the "BEST" in what your expectations are. Next is personal education on what you expect and are willing to pay for quality work with backing it up if not right.
Many choose to look as this as a hobby choosing to educate themselves how too do the work required and learn from the experience.
Everyone will have an opinion, make yours an educated one